We develop a stylized model that generates the following empirical predictions: the less (more) accessible the underlying market is ex ante, the more its liquidity improves (deteriorates) when basket trading becomes available. We empirically test these predictions using corporate bonds before and after the introduction of exchange-traded funds. Consistent with the model’s prediction, liquidity improvement is larger for highly arbitraged, low-volume, and high-yield bonds, and for 144A bonds to which retail investor access is prohibited by law. Our article leads to a more nuanced understanding of the impact of basket security introduction than previous research suggested.

Liquidity plays an important role in global research. We identify high-quality liquidity proxies based on low-frequency (daily) data, which provide 1,000× to 10,000× computational savings compared to computing high-frequency (intraday) liquidity measures. We find that: (i) Closing Percent Quoted Spread is the best monthly percent-cost proxy when available, (ii) Amihud, Closing Percent Quoted Spread Impact, LOT Mixed Impact, High–Low Impact, and FHT Impact are tied as the best monthly cost-per-dollar-volume proxy, (iii) the daily version of Closing Percent Quoted Spread is the best daily percent-cost proxy, and (iv) the daily version of Amihud is the best daily cost-per-dollar-volume proxy.