Using a unique dataset from the Shanghai Stock Exchange, we study the relation between daily open-to-close stock returns and order imbalances, and the commonality in order imbalances across individual, institutional, and proprietary investors. We find that institutional (proprietary) order imbalances have a larger price impact, but account for a significantly smaller proportion of daily price fluctuations. Commonality is much stronger for individual, rather than institutional (proprietary), order imbalances. Institutional (proprietary) investors favor large capitalization stocks, and co-movement in institutional (proprietary) order imbalances is stronger for these stocks.