AAPOApollo Global Management, Inc. (New)

Apollo earns chiefly from credit and insurance reserves rather than from buyouts.

Unlike classic private equity firms, the base here is debt: the company lends to businesses and finances assets, earning interest. That model is closer to banking in nature and markedly steadier than income from selling acquired companies.

The Athene insurance arm is the second pillar: it sells annuities and deploys the proceeds through Apollo's credit strategies. That provides a permanent inflow of capital for decades ahead, and it is why the company is increasingly compared to an insurer rather than a fund.

The risks follow: loan book quality in a downturn, asset-liability duration matching, and regulatory capital requirements for insurance. The company pays a regular dividend, unusual among private capital managers.