Why has local market concentration fallen as national concentration has risen?
Core argument: Between 1990 and 2014, industries with falling local concentration accounted for 72% of employment and 66% of sales, even as national concentration rose.
Recent data reveals a paradox in market concentration trends: while national concentration has increased, local concentration has decreased. This divergence is driven by large firms expanding into new local markets, which reduces local concentration and fosters competition. Between 1990 and 2014, industries with falling local concentration accounted for 72% of employment and 66% of sales. The Herfindahl-Hirschman Index (HHI) shows that local concentration declines are most pronounced in services, retail trade, and FIRE sectors. When top firms open new plants, local concentration drops and remains lower for at least 7 years, indicating that large firms do not dominate but rather enhance competition in local markets. This trend suggests a more competitive environment at the local level despite rising national concentration.

