Who Trades Index Rebalancings? Evidence on Benchmarking and Inelastic Demand

Benchmark index rebalancings are widely used to study non-fundamental demand shocks, but the underlying trading is rarely observed. Exploiting transaction-level data from the Colombian stock market and additions and deletions of stocks from MSCI international equity indexes, we trace who generates benchmark-driven demand, who absorbs it, and how it affects prices. Index demand extends beyond explicit index funds and ETFs: benchmarked but nominally active foreign institutions account for most rebalancing-driven trading. Domestic investors absorb most of the shock, while arbitrage capital plays only a limited role. We show that stock demand curves are steep, especially when retail participation is larger.