I'm not sure it has much to do this with, to be honest, largely because IPO's aren't really a pure supply and demand game. Many funds and groups will pick up IPO's purely as a 'just in case'. In fact, the number of individual investors who make up the pool of an IPO is very, very small. There isn't a single thing I can put my finger on in terms of why companies IPO much, much less than they used to, but I think Mark has one of the key ones with his cost/benefit points. It's a massive hassle to IPO now. It was always a hassle, but it's exponentially harder, more expensive and less likely to happen now than it ever used to be.