If you can’t inherit a billion dollars, the path to becoming a billionaire begins with a sales job or an engineering degree, a new study suggests.

The study released Monday from recruitment agency Aaron Wallis shows that of the top 100 richest people in the world, 10 began their careers as a salesperson and 22 studied engineering in school.

Of the 53 billionaires who began their careers working for another organization, 10 started out in sales and nine began trading stocks. Seventeen of the 100 richest billionaires started their own business while 30 inherited their wealth.

Among those who began their careers in sales, George Soros, the 29th richest person in the world, started his career as a travelling salesman for a toy company before making billions as a trader and broker.

Michael Dell, the founder of Dell computers, started working as a cold call salesman for a newspaper.

Of the top 100 billionaires, 75 have earned a degree, including 22 who have engineering degrees and 16 with business degrees. Engineering graduates include Jeff Bezos, the founder of Amazon and Larry Page, the co-founder of Google, while S. Robson Walton, Jim Walton and Alice Walton of Walmart fortune all have business degrees.

“Today we are seeing that nearly all of the top people in business are graduates and that a degree can be a great first-step into preparing you for your career ahead,” Rob Scott, managing director at Aaron Wallis Sales Recruitment, said in the report.

“It’s also unsurprising how many of the top 100 billionaires started working as salespeople, which can give you the communication and negotiation skills which are vital to succeed.”

Although the research suggests getting a degree is important, four of the top 10 richest people in the world—including Bill Gates and Mark Zuckerberg—do not have a post-secondary degree.

Aaron Wallis Sales Recruitment used Wikipedia, the Forbes list of the richest people on the planet and other sources to compile their list.