TPG Capital, one of the largest PE firms to retain its partnership structure, flirted with the idea of going public this year. Many of its peers are already publicly traded—Blackstone, KKR and Apollo Global Management, to name a few. But since going public, those firms' shares haven't performed very well, reportedly prompting TPG to scuttle its IPO plans altogether. And the firm has reason to. The lesson that Blackstone, Apollo and KKR have learned is that the public markets don't value the private equity business the way that they do. That may change over time, but up until now, equity analysts haven't seen eye to eye on PE stock valuations, perhaps because they cover PE as a subset of the broader financial services industry, where different rules apply.