How Efficient are Islamic Banks in Indonesia, Saudi Arabia, and the United Kingdom?

This research aims to analyze the efficiency level of 13 Islamic Banks in Indonesia, Saudi Arabia, and the United Kingdom from 2015 to 2019. The calculation of the efficiency level in this study is relative, not absolute. This study uses the Data Envelopment Analysis (DEA) method and source data from Bankscope and Bank Focus. This research consists of 3 input variables that are Total of Assets (X1), Staff Expenses (X2) and Total Deposit (X3), and 2 Output that is Income (Y1) and Loan (Y2). This research finds that the overall efficiency level of 13 Islamic banks in Indonesia, Saudi Arabia, and the United Kingdom are fluctuating. According to the result, the Islamic banks in Saudi Arabia is more efficient than in Indonesia and the United Kingdom. There are some inefficient variables—the solution for this inefficiency problem achieve by employing managerial simulation generated by DEA. This study implies that Islamic banks should reduce wasteful variables and optimize the variables that improve the efficiency.


Introduction
Many banking transformations have taken place from the start of standard human resource operations worldwide in recent years. This transformation has made a significant contribution to the performance of banks in the world. A functioning and healthy credit is not only crucial for the process of improving the economy of various markets but also can improve efficiency and operations, and can increase economic growth. Conversely, unhealthy banking will experience financial difficulties. Therefore, research into the factors that determine banking performance has attracted academic researchers and banking improvement.
According to Farrell (1957), to measure a bank's performance can be seen from the efficiency level, the company's efficiency consists of two components: technical efficiency and allocative efficiency. Although the conventional financial system still dominates worldwide, the Islamic banking system is quite interesting to researchers and banking practitioners' attention, and this evidence by the Islamic Banks that survived the crisis. Many countries (for example, the United Kingdom) have adopted the Islamic banking model because inherent characteristics are seen through real and transparent economic transactions free of interest, uncertainty, and gambling, and supported by assets (Belouafi & Chachi, 2014). Since the 2007-2009 financial crisis, many banking institutions have gone bankrupt, and many regulatory reforms are enacted. The 2008 subprime mortgage crisis found potential weaknesses of the conventional banking system and appeared to reveal Islamic banks (Mollah & Zaman, 2015).
When the 2008 global crisis, many financial institutions that collapsed, even financial institutions as big as Lehman Brothers, who were more than 100 years old, were not saved. However, it turns out that Islamic financial institutions can survive and even continue to grow amid the crisis, which is one reason why investment transactions in the Islamic financial system base on clear and real assets. Fourth, Islamic banks are free from the negative spread, which is the negative difference between deposit interest and loan interest. In other words, the interest that must be paid by the Bank to deposit customers is far greater than the interest on loans. This condition contributed to the banking sector is stuck in 1998. On the other hand, Islamic banks that are more profit-oriented are certainly free from the negative spread.
However, it does not mean that Islamic banking is without risk, if management does not work well, then there is a possibility that problems can occur. If there is a mismanaged Islamic bank, it will damage the public's view of the image of Islamic banking, the plan to develop Islamic banking can also disrupt, and its impact can worsen the world economy, this is where the need for research on factors that affect the overall performance of Islamic banking in the world.
In a study conducted by Sufian & Kamarudin (2015), examining Technical Efficiency (TE), Pure Technical Efficiency (PTE), and Scale Efficiency (SE) of domestic Islamic banks in Southeast Asia, namely Malaysia, Indonesia, and Brunei, compared to Foreign Islamic Banks from the Middle East in period 2006-2014. The study found that domestic Islamic banks are more efficient than foreign Islamic banks with a significance level of 1% and 5%. Overall domestic and foreign Islamic banks are less efficient in terms of operational costs, compliance with Islamic law, and double taxation to reduce Islamic banks' efficiency. (Detail shows in Table 1).  (Wahab, 2015). According to Hidayat (2014), one of Islamic banking's operational efficiency determines a very high cost and initial investment. This condition affects the low profits distributed to depositors. Besides, Islamic Bank financing equivalent rates are relatively higher than conventional bank loans. This condition can lead to decreased interest in financing customers in Islamic Banks (Syafrida & Aminah, 2015).
An increasing Amount (US Dollar) of literatures observed evaluating Islamic banks' efficiency by adopting different methods, such as profit efficiency, output efficiency, and costefficiency. There are mainly two components of efficiency analysis, i.e., technical efficiency and allocative efficiency, where the former maximize output with a given level of input, and the latter minimizes input for achieving a given level of output. The existing literature in efficiency analysis can divide into a few categories that measure the efficiency of merely Islamic banks or conventional banks by focusing on single or multiple countries (Hassan et al., 2018).
Based on previous research in Table 2, almost discuss Islamic banking's efficiency is still only in areas with the same characteristics. On a global scale, it is essential to compare wider regions. The difference between this study and previous research in the area of coverage is that this study compares three countries with different regions and characters: Indonesia, United Kingdom, and Saudi Arabia. The study's selection in the study was because these three countries list in the Top Islamic Global Financial Report (2019). The selection of Islamic banks in this study is based on banks that already have a reputation in the country and banks whose majority ownership is owned by the state.
Islamic banks in Indonesia have the character of using a dual banking system. In 2019, Indonesia became the top-ranking country in the 2019 Islamic Financial Country Index. The factors that led to its rise to the top were high-level political support from President Joko Widodo himself, who led the Sharia National Economic and Financial Committee (KNEKS) to promote Islamic finance in this country. Indonesia is also the largest economy with the largest GDP in the Organization of the Islamic Conference and the country with the largest Muslim population in the world. The development of regulations is also beneficial for this country with the collaboration between the Financial Services Authority and Bank Indonesia. Islamic banks in Saudi Arabia have the characteristics of a country system in the form of a kingdom. Saudi Arabia is one of the world's largest Islamic banking and financial markets. Saudi Arabia contributed significantly to Islamic financial assets totaling 1.6 trillion dollars. The Kingdom of Saudi Arabia is a member of the Gulf Cooperation Council, which has the most dominant economic conditions among the five other member countries, namely the United Arab Emirates, Qatar, Kuwait, Bahrain, and Oman. Saudi Arabia also received quite a lot of income apart from oil, namely from the Hajj and Umrah pilgrimage sector and the halal tourism sector, which was being developed to look for new income sources. Even so, Islamic banking is still control by a few people in Saudi Arabia. In 2019, Saudi Arabia was ranked 4th in the 2019 Islamic Financial Country Index.
The hallmark of Islamic banks in the UK is that although they are not Muslim-majority countries, the UK is the reference and center of Islamic world finance. The success and stability of the development of Islamic banks have attracted the attention of many parties. Several financial institutions in non-Muslim countries (such as United Kingdom, Luxembourg, and Switzerland) have also begun to accommodate the public and investors who want to carry out sharia financial transactions as long as they meet the requirements of the local financial authority. London's popularity as a center for Islamic finance emerged in 2013 when Prime Minister David Cameron announced plans to develop the British city as the financial capital of Western Islam. In 2019, the UK was ranked 17th in the Islamic Financial Country Index 2019. Therefore, it shows that previous research on efficiency measurement dominates by research with the same regional characteristics. This research tries to contribute this novelty by examining Islamic banks' efficiency in three countries with different regional characteristics but with the same Islamic bank category and size. Hence, the researcher seeks to compare Islamic banks' efficiency levels in Indonesia, Saudi Arabia, and the United Kingdom.

Methods
Farrell first introduced the Data Envelopment Analysis (DEA) in 1957 (Firdaus & Hosen, 2013). DEA is one of the analytical tools used to measure organizations' efficiency in profit-oriented and non-profit-oriented organizations where operations use several inputs to produce some outputs. The DEA technique makes efficient banking frontier sets and compares them with other inefficient banks. This technique does make scores or efficiency scores (Hidayat, 2014). Furthermore, the bank efficiency score limit between 0 and 1. The most efficient bank has a score of 1, while the bank with the most inefficient score is 0. Some research has discussed Islamic banking's efficiency level, such as Firdaus & Hosen (2013) and Wahab (2015). Research with the DEA method is to use domestically and abroad, as Almumani (2013) examined the efficiency of Islamic banking in Saudi Arabia and research conducted by Salami & Adeyemi (2015) levelof Islamic banking in malaysia international bank.
According to Tanjung & Devi (2013), the DEA method uses two commonly used model approaches, namely the Charnes, Chooper, and Roodes (CCR) model developed in 1978 and the Banker, Charnes, and Cooper (BCC) model in 1984. The first is the model Charnes, Chooper, and Roodes (CCR) This model was developed in 1978. The DEA-CCR model is known as the Constant Return Scale (CRS) model because it assumes that the production process follows the CRS. The CRS assumption assumes that each increase in one input will increase one output. This assumption applies to business units that have been producing at their maximum capacity (optimum scale). Then there is the Banker, Charnes, and Cooper (BCC) model, and the second model developed in 1984. This model assumes the Variable Return Scale (VRS), which is the previous model's development. The VRS assumption is that if there is an increase in one input, it will not affect the output increase because it does not operate at its optimal scale. The variables used for performance analysis by looking at efficiency are using input and output variables. The approach in this study is the intermediation approach. This approach views an institution as an intermediary, changing or transferring surplus units to deficit units. The model used in this study is the Constant Return to Scale (CRS). This study consists of 3 input variables: total assets, staff costs, and total deposits, and two outputs are revenue and loans. The main data source is secondary data obtained from Bankscope and Bank Focus, the data portal of bank financial statements worldwide with the same financial statement format and units equated in US dollars. This variable study's object includes 13 financial statements of Islamic Banks in Indonesia, Saudi Arabia, and the United Kingdom from 2015-2019. Measurement of efficiency with DEA is as follows (Rusydiana, 2013 Vik : the weighted weight of the input used for DMU k Zk : optimal value as an indicator of the relative efficiency of subDMU k DEA has several managerial values. First, DEA results in efficiency for each Decision-Making Unit (DMU), relative to the other DMUs in the sample. This efficiency figure allows an analyst to recognize the DMU most in need of attention and plan corrective actions for DMU, which is less efficient. Second, the DEA shows a number DMU which has excellent efficiency and a set of multipliers that can be used by the policymaker to devise an improvement strategy, so that a decision-maker policy not only recognizes inefficient DMUs but also knows how much inputs and outputs that must adjust in order to have high efficiency. Third, DEA provides a cross-efficiency matrix. The cross efficiency of DMU A to DMU B is the ratio of Weighted output divided by weighted input calculated using input levels and DMU A outputs and DMU B input and output weights. Cross efficiency analysis can help one policymaker recognize efficient DMUs but use a combination of inputs and resulting in a combination of outputs that are very different from other DMUs.

Result and Discussion
Based on the efficiency analysis results using the Data Envelopment Analysis (DEA) analysis tool, with the Warwick Win DEA software and Islamic bank financial statement data sources from bank scope and bank focus, each Islamic Bank's efficiency values are as shown in Figure 1. Based on Figure 1, the classification of efficiency categories in this study is divided into three parts: the Green, Amber, and Red categories. Green range is 100%, amber range is 90% -99.99% and range red is 0% -89.99%. Understanding the Green classification is an Islamic bank in an efficient condition and must be maintained in the following year. The understanding of the Amber classification is an Islamic bank is approaching an efficient point. However, it might also be risky if the inefficiency problem, not addresses, and attention is needed. Understanding Red's classification is a risky Islamic bank because it is far from an efficient limit to achieve. Here, management action is immediately needed to improve inefficiency from calculating Islamic banks' efficiency in Indonesia, Saudi Arabia, and the United Kingdom as many as 13 Islamic banks in 2015-2019.
Data Envelopment Analysis can provide repair values for units that experience inefficiency, then banks that experience inefficiency can be calculated based on managerial simulations conducted by the DEA.

Gatehouse Islamic Bank United Kingdom
During the years from 2015-2019, the Gatehouse Syariah Bank UK's efficiency level reached 100% in 2015, 2016, and 2017 but experienced an inefficiency in 2018 of 27.29% due to inefficiencies in the fixed assets variable, staff expenses, and total deposits and loans. In 2019 the value was 32.85% inefficiencies occurred in fixed assets, staff expenses, and total deposits and income. The average efficiency is 72.028%. The efficiency improvement of the UK's 2019 Islamic gatehouse bank shows in Figure 2. Based on Table 3. Gatehouse Bank PLC (Gatehouse) is an official bank in the UK, based in Mayfair, London. Founded in 2008, the bank operates according to Shariah principles and offers savings and financial products for commercial and residential real estate in the UK and seeks and advises UK real estate investors focusing on development for rent or lease in the private sector. The efficiency value obtained by the Gatehouse Islamic bank UK 2019 is 32.85 percent (see Figure 2). This result includes the red category, which means that Islamic banks are at risk because they are far from the efficient limit. Through a detailed calculation, the Gatehouse Bank UK experienced inefficient waste in fixed assets, staff expenses, and total deposits. It shows the difference in actual data that does not balance with the target data or its ideal form. Spending on fixed assets must be reduced by 83.0 percent, while expenses for staff expenses must reduce by 91.0 percent, and total deposits must reduce to 67.1 percent. Through the same weighting, Gatehouse Islamic Bank United Kingdom 2019, it should be able to get income 403.8 percent more than what happened, while in terms of Loans, it is following the actual Amount (US Dollar) and target. This insignificant result of Gatehouse bank United Kingdom is relevant to Öndeş (2019). Their study shows an insignificant result for the UK, including Gatehouse Bank, and significant in Turkey Islamic banks in asset quality and management quality.

Al-Bilad Islamic Bank Saudi Arabia
Based on Table 4, during five years from 2015-2019, the efficiency level of Islamic Bank A-Bilad Saudi Arabia has fluctuated, reaching 80.66% in 2015 due to inefficiencies in fixed assets, staff expenses, and total deposits, reaching 86.36% in 2016. variable, fixed assets, staff expenses, and total deposits, reaching 89.61% in 2017, there was an inefficiency on the fixed assets variable, staff expenses, and total deposits and income, reaching 82.27% in 2018 inefficiency on the fixed assets variable, staff expenses, and total deposits and income, and 71.56% in 2019 incurred inefficiencies on fixed assets, staff expenses, and total deposits variables. The average total efficiency is 82.092%. 248 Al Bilad Bank is a Saudi Islamic bank that establishes in 2004. The efficiency value obtained by Al-Bilad Islamic Bank of Saudi Arabia in 2019 based on DEA calculation shows 71.56 percent and includes in the Red category. This calculation means that Islamic banks are at risk because it is far from the efficient limit to achieve. With this condition, management action immediately needs to improve efficiency. In 2019 Saudi Arabia Al-Bilad Islamic Bank experienced inefficient waste in fixed assets, staff expenses, and total deposits through a detailed calculation. Spending on fixed assets must be reduced by 28.4 percent, while staff expenses must reduce to 28.4 percent, and total deposits must reduce to 28.4 percent. Through the same weighting, Al-Bilad Saudi Arabia Islamic Bank 2019, in terms of income and Loans are following the actual Amount (US Dollar) and target. Miah & Uddin (2017), that study about the comparative study between Islamic and conventional banks efficiency in GCC, said that Al-Bilad Bank also have some inefficient results in recent years, but there is much room for Islamic banks to increase their productive efficiency, like from cost-efficiency. This finding supports earlier studies from Hassan et al. (2018) that try to measure Islamic banks' performance in Saudi Arabia. Bank Al-Bilad is found least efficient in decreasing costs by decreasing input for achieving a particular output level. The findings are consistent with Almumani (2013) that bank Al Bilad is relatively less efficient in technical efficiency.

BLME Islamic Bank United Kingdom
Based on Table 5, during five years from 2015-2019, the efficiency level of the UK BLME Islamic Bank has fluctuated. In 2015 the values reached 84.06% due to inefficiencies in fixed assets, staff expenses, total deposit, and income variables. The value was reaching 93.74% in 2016. There was an inefficiency in the fixed variable. assets, staff expenses, and total deposits. For 2017, the value is 57.03%, there were inefficiencies in fixed assets, staff expenses, total deposits, and income variables. In 2018, the calculation reaching 59.51%. There were inefficiencies in fixed assets, staff expenses, and total deposit and income. Finally, in 2019, the value reached 74.26% due to the fixed assets' inefficiencies, staff expenses, total deposit, and income variables. The average total efficiency was 73.72%. The efficiency improvement of the UK BLME Islamic bank 2019 shows in Figure 3.

Figure 3. Efficiency Improvements to the BLME UK Islamic bank 2019
Source: Data processed by Warwick Win DEA BLME (Bank of London and The Middle East Plc) is an independent wholesale Islamic bank independent from the UK and is the largest Islamic Bank in Europe. The efficiency value obtained by the UK BLME Islamic bank 2019 based on DEA calculation shows 74.26 percent and include in the Red category, which means that Islamic banks are at risk because it is far from the efficient limit to achieve. Here management action is immediately needed to improve inefficiency. A detailed calculation shows that the 2018 BLME UK Syariah Bank experienced inefficient waste in fixed assets, staff expenses, and total deposits. Spending on fixed assets must be reduced by 44.0 percent, while staff expenses must reduce to 68.6 percent, and total deposits must reduce to 25.7 percent.
Through the same weighting of the UK BLME Islamic bank 2019 in terms of income, 3195.0 percent of the actual data must be added. This condition is because the UK BLME Islamic bank categorizes as just beginning to develop in the UK, while in terms of the loan, it is following the actual number and target. The efficiency value of BLME banks in the previous year from 2015-2019 was relatively quite efficient. This value is relevant because BLME became the Best Islamic Bank in Europe (2008) and Best Islamic Bank in the UK (2009, 2010, 2011, 2012, and 2013). This result is relevant to the study of Khan (2009) about the profitability of conventional and Islamic banks in the UK. The study finds that Islamic banks in the United Kingdom, including BLME Islamic Bank, are less geared, less liquid, but more efficient in terms of their capital than the Conventional banks and the Conventional banks are more stable than Islamic banks.

Al-Jazira Islamic Bank Saudi Arabia
Based on Table 6, during five years from 2015-2019, the overall efficiency level of Islamic Bank Al-Jazira has shown a good trend, reaching 100.00% in 2015, 99.77% in 2016 due to inefficiencies fixed assets, staff expenses, and total deposit variables. Back 100.00% efficient in 2017, down to 94.39% in 2018 due to inefficiencies in fixed assets, staff expenses, total deposit, and income variables, and 92.38% in 2019 due to inefficiencies fixed assets variable, staff expenses, and the total deposit. The average Amount (US Dollar) of efficiency is 97.30%. Improvements in the efficiency of Islamic Bank Al-Jazira Saudi Arabia 2019 shows in Figure 4. 252 Bank Aljazira recognize as one of the leading fast-growing sharia financial institutions in Saudi Arabia, a Saudi-oriented and client-oriented Financial Group that provides individuals, businesses, and institutions with innovative financial services according to Sharia through the professional and dedicated staff. The efficiency value obtained by Al-Jazira Bank of Saudi Arabia in 2019 shows 92.38 percent and belongs to the Amber category, meaning that the Islamic Bank is approaching the point of efficiency. However, it may also be risky if inefficiency problems, not addresses, and attention are needed.

Al Rayan Islamic Bank United Kingdom
Based on Table 7, during five years from 2015-2019, Al-Rayan Islamic Bank UK's overall efficiency level has experienced a pretty good efficiency trend, reaching 100.00% in 2015, 100.00% in 2016, 100.00% in 2017, reaching 80.76% in 2018 due to inefficiency of fixed assets, staff expenses, total deposits, and loans. In 2019, the value reached 94.52% due to inefficiencies in fixed assets, staff expenses, total deposit, and loan variables. The average Amount (US Dollar) of efficiency is 95.05%. Improvements in the efficiency of the British Al-Rayan Islamic bank 2019 shows in Figure 5.
Al Rayan Bank PLC (formerly known as Islamic Bank of United Kingdom) is a commercial bank in the UK that offer sharia-compliant financial service products to customers of any religion. This bank is the first British Bank to claim to operate, as a whole, following Islamic principles. Based on the DEA calculation showing a figure of 94.52 percent and included in the Amber category, Islamic banks are approaching the point of efficiency. However, it may also be at risk if the inefficiency problem not handles, and attention is needed here.

Etikonomi
Volume 19 (2), 2020: 237 -270 A detailed calculation shows that the Al-Rayan Islamic bank of England in 2019 experienced inefficient waste in fixed assets, staff expenses, and total deposits. Spending on fixed assets must be reduced by 5.5 percent, while staff expenses must reduce to 84.9 percent, and total deposits must reduce to 83.3 percent. Through the same weighting of Al-Jazira Saudi Arabia Syariah Bank 2019 in terms of income, it is by the actual Amount (US Dollar) and target, while in terms of Loans, it must be increased again by 45.3 percent. According to Öndeş et al. (2019) also said Al-Rayan Islamic bank UK is almost efficient. The other factor that could make Al-Raryan Islamic bank almost efficient is because Al-Rayan Islamic bank is the most prominent Islamic Bank in the United Kingdom.

. Improvements in the Efficiency of Al Rayan Islamic Bank of UK 2019
Source: Data processed by Warwick Win DEA

Alinma Islamic Bank Saudi Arabia
Based on Table 8, during five years from 2015-2019, the overall efficiency level of Alinma Islamic bank has been outstanding, reaching 100.00% from 2015-2019, the average Amount (US Dollar) of efficiency is 100.00%. The future suggestion is that Alinma Islamic Bank Saudi Arabia must maintain this condition in the following year. The efficiency score of the Alinma Saudi Arabian Islamic bank 2019 shows in Figure 6. which means that Islamic banks are in an efficient condition in terms of fixed assets, staff expenses, and total deposits, income and loans are in accordance between the actual number and the target. These results are consistent with research conducted by Hassan et al. (2018) that try to measure Islamic banks' performance in Saudi Arabia. The result said that overall, Alinma Bank Saudi Arabia has good efficiency.

Al-Rajhi Islamic Bank Saudi Arabia
Based on Table 9, the efficiency level of Al-Rajhi Islamic Bank as a whole experienced a good efficiency trend, which reached 100.00% in 2015, 100.00% in 2016, 100.00% in 2017, decreased to 87.47% in 2018 due to inefficiency in fixed assets, staff expenses, and total deposits, and 100.00% in 2019. The average Amount (US Dollar) of efficiency is 97.49%. The efficiency score of Al-Rajhi Saudi Arabian Islamic Bank 2019 shows in Figure 7. Al Rajhi Bank, founded in 1957, is a bank originating from Saudi Arabia and is the largest Islamic bank in the world by capital. The efficiency value obtained by Al-Rajhi Islamic Bank of Saudi Arabia in 2019 based on DEA calculation shows 100.00 percent and include in the Green category. This result means that Islamic banks are efficient in terms of fixed assets, staff expenses, and total deposits, income, and loans. This fact shows no difference between the actual data (blue graph) and the target data or its ideal form (orange graph). According to the actual number and the target, the condition must maintain in the following year. The result is not surprising since many studies like from Hassan et al. (2018) have found that overall results summarize that Al-Rajhi is most efficient in Saudi Shari'ah compliant banking industry as commemorating a mean efficiency score followed by Al-Jazira and Al-Inma Bank, and AlRajhi also one of the most prominent Islamic Bank in Saudi Arabia.  The efficiency value obtained by Bank of BCA Sharia Indonesia 2019 based on DEA calculation shows 100.00 percent and include in the Green category. This result means that Islamic banks are efficient in terms of fixed assets, staff expenses, and total deposits, income, and loans. This study's results contradict previous research by Bayuny & Haron (2017), that find the overall value of BCA Syariah Bank has not had a good enough efficiency in recent years.

Bank of BNI Sharia, Indonesia
Based on Table 11, over the five years from 2015-2019, the overall efficiency level of Bank BNI Syariah Indonesia has an excellent trend of efficiency, reaches 100.00% from 2015-2019. The average efficiency is 100.00%. Bank BNI Syariah Indonesia 2019 efficiency score can be seen in Figure 8. Finally, after ten years passed, on June 19, 2010, following the BI Governor's decree, BNI Syariah was separated from conventional banks.
The efficiency value obtained by Bank BNI Syariah Indonesia 2019 shows 100.00 percent and include in the Green category. This result means that Islamic banks are in an efficient condition in terms of fixed assets, staff expenses, total deposits, income, and loans following the Amount (US Dollar) actual and targe. This condition shows no difference between the actual data and the target data or its ideal form. These conditions must maintain in the following year.  Havidz & Setiawan (2015) that find that BNI Sharia has good efficiency due to the assets in Indonesia.

Bank of BRI Sharia, Indonesia
Based on Table 12, the efficiency levels of BRI Sharia Indonesia Bank as a whole has a good trend, reaching 100.00% in 2015, 100.00% in 2016, decreasing to 99.56% in 2017 due to inefficiencies in fixed assets, staff expenses, total deposit, and income. The value reached 100.00% in 2018 and 2019. The average efficiency is 99.91%. Bank of BRI Sharia Indonesia 2019 efficiency score can be seen in Figure 9.  262 data (blue graph) and the target data or its ideal form (orange graph). These conditions must maintain in the following year.
These results are consistent with Sufian & Kamarudin (2015), showing that the Bank of BRI Sharia has a good efficiency. Because BRI Sharia is one of the banks with the most considerable assets and has human resources inclusive to the regions, these results are also relevant to previous research conducted by Zuhroh et al. (2015). who researched the cost efficiency of Islamic banks in Indonesia said that Bank of BRI Sharia Bank has good inclusiveness and good value trend efficiency. Table 13 shows that the efficiency levels of Bank Bank of Sharia Mandiri as a whole the efficiency trend has fluctuated. The value reaching 68.88% in 2015, 76.69% in 2016, 100.00% in 2017, 100.00% in 2018, and 100.00% in 2019. The average total efficiency was 89.11%. Bank of Sharia Mandiri bank efficiency scores 2019 shows in Figure 10. The efficiency value obtained by Bank of Sharia Mandiri 2019 based on DEA calculation shows 100.00 percent and include in the Green category. According to the Amount (US Dollar) actual and target, this value means that Islamic banks are in an efficient condition in terms of fixed assets, staff expenses, total deposits, Income, and Loans according to the Amount (US Dollar) actual and target. This condition shows no difference between the actual data and the target data or its ideal form. These conditions must maintain in the following year. This result is not surprising because it agrees with previous research conducted by Widiarti et al. (2015) and Hidayati et al. (2017). The research finds that Bank of Sharia Mandiri is experiencing a relatively good trend of efficiency. One of the factors is because it has quality resources. including Rasmala Bank, one of the factors was because Rasmala Bank UK's assets were still small. However, These results also prove that the assets' size does not necessarily affect the efficiency value.

Conclusion
This research calculates the efficiency of 13 Islamic banks in Indonesia, Saudi Arabia, and the United Kingdom for the 2015-2019 period. The result shows that in 2015 there were ten efficient Islamic banks and three Islamic banks experiencing inefficiency. In 2016 there were nine Islamic banks that efficient and four Islamic banks that experience inefficiency. There were ten Islamic banks that efficient and three Islamic banks that inefficient in 2017. In 2018 there were seven Islamic banks that efficient and six sharia banks that were inefficient. Finally, in 2019, there are eight efficient Islamic banks and five inefficient Islamic banks. During the 2015-2019 period, each Islamic Bank in Indonesia, the UK, and Saudi Arabia had different efficiency levels.
Some variables are inefficient, like from total assets, staff expenses, and total deposit variables. The 100% efficient rate shows that Islamic banks have been right in allocating production factors compared with other Islamic banks. Specific results obtained through managerial simulations indicate that Islamic banks can be improved to be efficient in the future. The efficiency levelof an inefficient Islamic bank base on its variables. If labor expenditure is inefficient, then the number of workers handling Islamic banks is too much. To overcome inefficiencies in the workers can be done by adding production aids. Inefficiencies in total assets and total deposits state that the Islamic banks are relatively wasteful in allocating them.
Inefficiencies in income and loans indicate that the Islamic Bank produces relatively less income and loans than other Islamic banks, where efficient Islamic banks can produce more with the same input and output ratio. The inefficiency of staff expenses indicates that Islamic banks' inefficient workers are relatively less productive than Islamic banks whose workers are efficient.
Based on the results of the study's conclusions and limitations, suggestions that can be submitted to improve efficiency are: First, reducing the workers of inefficient Islamic banks. Second, reallocating wastage of total variables assets and total deposits. Third, implementing policies that can result in increased income and loans. Fourth, this research should be preceded by local-level research to obtain an average picture of input and output allocations so that data accuracy is better than before. Fifth, Islamic banks can use this research to reduce wasteful variables like the number of workers and staff cost efficiency and optimize those that are still less than optimal, like income and loan to achieve efficiency.