Some people may tell you that extreme wealth is a matter of hard work, determination, education, opportunity, and a little bit of luck. While all that may be true, a recent study by Forbes reveals becoming a self-made billionaire may be anything but a random set of circumstances.

The study, which focused on the 274 self-made billionaires on Forbes’ list of the 400 wealthiest Americans, found that a significant percentage of them had these four traits in common:

1. Parents with a tremendous aptitude for math: It turns out being a billionaire requires a lot of left-brain thinking. Who knew, right? But the reality is a high number of self-made men and women had parents with engineering, accounting, or finance-based backgrounds.
2. Autumn babies: Timing is everything, or so it would seem. According to Forbes, more self-made billionaires were born in the fall than any other season of the year. In fact, a specific concentration of them were born in September. On the other hand, almost none were born in December.
3. High dropout rate: Almost 15% of the billionaires on Forbes‘ list either never started or never finished college. How’s that for the power of independent thinking? That percentage is largely due to tech geniuses like Bill Gates, Steve Jobs, Michael Dell and Mark Zuckerberg, who were way ahead of the curve when it came to tech-related majors.
4. Know what it feels like to lose: Several billionaires were a part of business ventures that failed miserably early in their careers. But they learned from the experience and knew which mistakes not to make the next time around.

Of those billionaires who weren’t necessarily self-made (by that, we mean they may have come from families who had millions, not billions), several had these three rites of passage in common:

1. Goldman Sachs: Want to get rich? Go to Goldman Sachs. At least 11 current billionaires did just that on their way to 10-figure incomes.
2. An Ivy League graduate degree: Half of the billionaires on the list who derived their fortunes from finance have graduate degrees. Almost 70% of those graduate degrees came from Harvard, Columbia or Wharton.
3. Skull and Bones: Yep, it’s true. Several of the world’s richest men were members of Yale’s super-secret society. Mind you, most of these men are not self-made billionaires. But they are millionaires, nonetheless.

Source: “A Recipe for Riches,” by Duncan Greenberg, Forbes, 10/09/09.