Few investments offer as much liquidity as publicly traded stock. Almost by definition, liquidity requires that a firm’s shares be held by a large number of owners, many of whom are only temporary. It is often argued that managers will inevitably fail to serve the interests of such shareholders; originally by Smith (1776) and Berle and Means (1932) and more recently in debates over the virtues of “relationship investing” in countries such as Germany and Japan (Coffee, 1991; Roe, 1994; Bhide, 1993). Admati, Pfleiderer and Zechner (1994) show formally how liquid markets undermine governance by providing investors with the option of easy exit. Other theoretical models, however, come to the opposite conclusion; liquidity can reduce agency problems. Building on Hayek’s (1945) insight that market prices provide information as well as terms of trade and the Kyle (1985) model of ‘informed’ trading, Holmstrom and Tirole (1993) show how liquidity can improve incentive contracts by increasing the information content of stock prices. A more liquid market allows informed observers of executive ability to drive the stock price closer to fundamentals by hiding their trades more effectively in the larger order-flow provided by uninformed noise traders.
The more effective are these trading “external monitors” in incorporating managerial ability and actions in the stock price, the greater the incentive the board has to tie executive performance to the now more informative stock price. Generally, executive stock options are the tying device most closely related to stock appreciation rights modeled by Holmstrom and Tirole. A complementary argument appears in Kyle and Vila (1994), Kahn and Winton (1998) and Maug (1998) who demonstrate that liquidity can reduce the costs that an investor bears in taking a large position in order to influence or replace managers, as originally suggested by Manne (1965).