No, it's actually true, they are quite stable. What they lack though is outliers in terms of success. They tend to be quite conservative and as a consequence they are risk averse and tend to play it safe. For a high return you need a different appetite for risk. Of course the key to a different risk appetite is to be able to externalize the negatives of that risk but to be able to reap the rewards. Such asymmetric bets are at the root of most successful business empires, you'd never see them in a co-op.