Many entrepreneurs, and the venture investors who back them, seek to build billion-dollar companies.

Why do investors seem to care about “billion dollar exits”? Historically, top venture funds have driven returns from their ownership in just a few companies in a given fund of many companies. Plus, traditional venture funds have grown in size, requiring larger “exits” to deliver acceptable returns. For example – to return just the initial capital of a $400 million venture fund, that might mean needing to own 20 percent of two different $1 billion companies, or 20 percent of a $2 billion company when the company is acquired or goes public.