Does issuer composition change as stock markets grow, and, if so, how An increase in market capitalization may be driven by growth on the intensive or extensive margin. Such growth may also influence the level of market concentration and diversity among listed firms. Using a novel dataset, this paper examines how the number, concentration, and sectoral diversity of issuers change as domestic stock markets grow, with a focus on low- and middle-income countries. The results show that an increase in stock market capitalization tends to be associated with only growth on the intensive margin. Greater market activity, however, is linked to entry of new issuers and for low- and middle-income countries, also to marginally lower market concentration. However, there is no evidence that sectoral diversity changes with market size or activity. These findings have important implications for firm financing as stock markets may not necessarily become more inclusive as they grow.