This paper analyzes the evolution of the Lerner index for Costa Rican banks between 2008 and 2019. We document a significant drop in market power during this period, which we relate to less concentration in loans and deposits. The market became less consolidated as a fringe of 29 small banks gained market share at the expense of large and medium banks. We find that for individual banks, a greater market share of loans, and greater loan specialization are related to higher profitability, while a greater market share of deposits and greater size are related to lower profit margins.