By Jade Scipioni

There are only about 2,200 billionaires in the world — or 0.0002% of planet’s population.

And 67% of those billionaires are self-made.

The members of that self-made group generally made their money in one of a few ways: they invented a useful product (think Bill Gates with Microsoft, whose net worth is around $107 billion); they innovated a new way of solving a problem (think Airbnb co-founder Brian Chesky, whose net worth is around $3.7 billion); or they are savvy investors (think Warren Buffett, worth $87.3 billion). Indeed, climbing the corporate ladder will rarely get you into the club (Tim Cook who runs nearly $1 trillion company Apple, for example, is worth around $625 million).

But beyond sharp entrepreneurial and investing chops, self-made billionaires share some traits, according to according to Rafael Badziag, who interviewed 21 of them (including early Uber investor Tim Draper and InfoSpace and Viome founder Naveen Jain) for his book, “The Billion Dollar Secret.” Here are three of the top things they have in common, according to Badziag.

1. They succeed no matter what the ‘weather’ is

Badziag says it’s clear why most of the general population (he calls them “drifters”) don’t succeed in life: They are waiting for conditions to be perfect before they strike, and often those ideal conditions never materialize so they don’t fully pursue their dreams.

“Self-made” billionaires, he says, are different. Most of the billionaires Badziag interviewed didn’t come from well-off families or ideal situations, but they pursued their dreams no matter the circumstances around them — no matter the “weather outside or inside,” he says.

Take for example, one of the billionaires Badziag interviewed: N.R. Narayana Murthy, who co-founded IT giant Infosys, which is valued at more than $45 billion.

The 72-year-old, who is now worth as estimated $2.4 billion, grew up in India in ’50s and ’60s, a poor country that he says was one of the most hostile to free enterprise at the time. As a child, his family was so poor he had to sleep on the floor because they had no furniture.

But despite having no money, Murthy was eager to learn; he would go to the public library in town (he lived outside Karnataka) and read everything he could. From what he learned, Murthy believed software was the future, so in 1981 he and some colleagues got the idea to create a software company. But they didn’t have a computer, and at the time, the Indian government required a license to import one, he told Badziag. So for three years, Murthy back and forth to Dehli by train, 1,500 miles each way, making at least 50 visits to pitch officials on why he should be granted a license. With their computer and phone line (which he says took a year to procure), Murthy and his co-founders started Infosys and grew it from an operation with seven employees into a global business and one of the leading technology consulting companies in India.

2. They don’t do it for the money

Most “drifters” are dying to have big incomes but never quite achieve a high net worth status, or if they do, they lose motivation when they have some good in money in bank, says Badziag. (He refers to it as “the gold digger’s trap.”)

However, Badziag found that the “self-made” billionaires he interviewed aren’t motivated by wealth. Instead, they “have a strong sense of purpose and passion for their work,” and are motivated by a desire to “to grow and learn no matter how big their bank accounts get,” he says.

As Apple founder Steve Jobs once famously said, “I was worth over a million dollars when i was 23 and over $10 million when I was 24, and over $100 million when I was 25. And it wasn’t that important, because I never did it for the money.” Jobs said he started Apple with a simple vision of trying to create a “computer in the hands of everyday people. ” and they ended up succeeding beyond they wildest dreams.

Murthy told Badziag he was driven by the belief that the only way to solve the problem of poverty was “through the creation of jobs with good incomes and that entrepreneurship was the best instrument for such a solution.”

And French-Syrian businessman Mohed Altrad, who made his now $2.7 billion fortune by acquiring a scaffolding company in France in 1985 and growing it into the industrial services giant Altrad Group, told Badziag that he doesn’t view money as an objective.

“It’s one of the signs of success. The success of the organization is to be sustainable, in which people are happy, in which humanity finds its foundation,” Altrad said.

3. They are frugal

“Drifters” love spending money, according to Badziag, often going into debt to spend even more than they have. Even successful people are prone to showcasing their wealth via cars, expensive clothes and lavish vacations.

But the billionaires Badziag interviewed were different: They “get pleasure making money, but don’t enjoy spending it,” he says.

Take for example, Warren Buffett, the fourth-richest person in the world with a net worth of around $87.3 billion. Despite his massive wealth, the 88-year-old still lives in the same modest Omaha house he purchased in 1958 for $31,500 (which is around $277,00 in today’s dollars). He also keeps his breakfast budget low, only spending around $3.17 a day at McDonald’s to get one of three items: two sausage patties, a sausage, egg and cheese or a bacon, egg and cheese.

And Peter Hargreaves, the founder of Hargreaves Lansdown, one of the UK’s largest financial services businesses, told Badziag a few years back that he was still driving an eight-year-old Toyota Prius. Hargreaves’ net worth is estimated at $4.2 billion.

Hargreaves also told Badziag that his children were frugal too. ”[My kids] drive very modest cars; they both have a car that’s seven years old. They both have quite modest flats. And if they go on holiday, they go with their mates, and they go to the back of the plane,” Hargreaves said.

Of course, some billionaires adjust to their level of wealth. For example, though Bill Gates is famous for wearing a $10 watch, he recently admitted that he also indulges: “Now I take lots of vacation. My 20-year-old self is so disgusted with my current self. You know, I was sure I would never fly anything but coach and you know, now I have a plane,” Gates said last month at a Village Global event.

This article first appeared on CNBC https://www.cnbc.com/2019/07/02/self-made-billionaires-have-these-traits-in-common.html and is republished with its permission.