The size variable is introduced to capture potential economies or diseconomies of scale in the banking sector. This variable controls for cost differences and product and risk diversification according to the size of the credit institution. The first factor could lead to a positive relationship of the size with bank profitability if there are significant economies of scale, while the second to a negative one if increased diversification leads to lower risk and thus lower required returns. (Panagiotis et al, 2007)