It is a formulaic process that determines which lawyers reach the very top of one of the world’s largest and most lucrative law firms. Yet little is known about the way partners enter the equity tier at Kirkland & Ellis.

Success can mean a partner overnight jumps from a fixed salary to the opportunity to earn up to tens of millions of dollars a year. Kirkland’s average profits per equity partner are among the highest of any commercial law firm, at $7.39 million, beaten only by New York’s Wachtell, Lipton, Rosen & Katz.