On information efficiency and financial stability

We study a simple model of an asset market with informed and non-informed agents. In the absence of non-informed agents, the market becomes information efficient when the number of traders with different private information is large enough. Upon introducing non-informed agents, we find that the latter contribute significantly to the trading activity if and only if the market is (nearly) information efficient. This suggests that information efficiency might be a necessary condition for bubble phenomena, induced by the behavior of non-informed traders, or conversely that throwing some sands in the gears of financial markets may curb the occurrence of bubbles.