Smarter people are not richer – and that’s a rule!

Education, perhaps? Opportunities and opportunities. Rich parents can make a big difference.

Maybe intelligence? It makes sense: almost every highly successful businessperson is smart.

But that's a correlation, not causation. When Nobel Prize-winning economist James Heckman asked people how big a role innate intelligence plays in financial success—how much the difference between your income and mine, for example, is based on our relative IQs—most people said 25 percent. Some went up to 50 percent, reports Investor.

But they are wrong.

Heckman's research found that innate intelligence plays, at best, a 1 to 2 percent role in a child's future success. Instead, financial success is correlated with the personality traits that make up conscientiousness: self-discipline, perseverance, and diligence.

The study's findings align well with Mark Cuban's take on what contributes most to success:

"It's not about money or relationships. The secret is in the willingness to surpass everyone and constantly learn", he stated.

Of course, luck also plays an important role in success. As the authors of the Cornell study wrote: “Maximum success never coincides with maximum talent, and vice versa. Our simulation clearly shows that such a factor is just pure luck.”

But you can't control luck.

And you can only partially control IQ. While you can certainly become more educated, fluid intelligence—the ability to think logically and solve problems independently of acquired knowledge—cannot be acquired.

But what you can control is how conscientious you are. How valuable you are. How persistent you are.

How hard you work - and how hard you try to learn.

Definition of success

Everyone defines success differently, as they should. But if you happen to define success by traditional metrics, such as professional accomplishments or wealth or fame, hard work is a great equalizer.

On the other hand, if your definition of success relies heavily on the quality of personal relationships, maintaining a positive work-life balance, or making a significant difference in the lives of others, hard work is still a great equalizer. Great relationships take significant effort. A balance between work and private life requires considerable effort. Making a significant difference in other people's lives requires significant effort.

People who make the most of their lifespans work hard to improve the quality of the hours they have. People who excel at helping others work harder to use their skills and experiences; that is how they can make a significant difference.

We cannot control whether we possess certain inherent advantages. But we can control our level of persistence, self-discipline, and diligence. You control how wisely we work to be satisfied. We can choose to work and learn.

These are things you can control.

Which is great, because science says those things will have the biggest impact on your success.