George Roberts

Henry Kravis, George Roberts and Jerome Kohlberg started the firm back in 1976 and achieved fame by making hefty profits from leveraged buyouts. Today, its business is much broader as it makes its NYSE trading debut.

As private-equity giant KKR moves at last toward completing its own IPO, it is opening up its internal finances to the SEC. One of the more interesting items: How little its two billionaire founders, cousins Henry Kravis and George Roberts, earned from the business last year.

Now that private equity is no longer producing monster returns, it's time to assess its value. By using debt, buyout shops have taken over struggling companies and enriched investors. But critics say the practice leads to more layoffs and the "flipping" of companies.