How can you predict who will have a high income? Of course, that’s a complex question, as there are countless variables, including education level, age, race and others.

In a recent study, a team of researchers from Temple University set out for an answer. Their research identified several factors that determine future affluence and ranked them accordingly.

The study is the first to give a validated rank ordering of these factors.

The study is published in Frontiers in Psychology.

“Our research was motivated by reading the existing research that noted all sorts of things predicted income,” said William Hampton, the study’s lead author, who is now a postdoctoral researcher at the University of St. Gallen in Switzerland. “This includes some common-sense ones, such as their education, or occupation, as well as some less obvious factors like one’s height (taller people earn more).”

“But no one seemed to be able to say what was more important than what,” he continued. “Particularly, we knew that this behavioral variable, delay discounting, was also predictive, but we were really curious how it would stack up against some more common sense variables like education and age.”

In all, the study examined nine factors, which accurately predicted income, on average, in the following order: occupation, education, zip code, gender, delay discounting, ethnicity, height, age and race.

“Delay discounting” describes a person’s ability to resist instant gratification. In contrast to factors like education, occupation and gender, delay discounting is a behavioral variable that describes self-control.

In the 1960s, this characteristic was famously measured in a series of studies called the Stanford marshmallow experiment, in which children were offered a choice between one treat — a marshmallow, for example — or, two treats, which they would receive if they were able to resist eating the treat while the tester left the room for a short period of approximately 15 minutes.

In follow-up studies, the Stanford researchers found that the children who were able to wait for the reward typically went on to have better life outcomes, measured by factors like SAT scores and educational attainment.

So, going into the new study, the researchers knew that delay discounting would likely play a role in income level. They did not anticipate, however, that it would actually be more predictive than factors like age and race.

“The methods historically used by psychologists, such as correlations and regression, did not allow for this simultaneous comparison of these different kinds of factors,” said Hampton.

“Our results were interesting because when we compared the importance of these factors, we found that how much a person discounts the value of future rewards compared to immediate ones (known as delay discounting) was more predictive of income than some other ‘big’ variables such as age, ethnicity and race.”

To measure delay discounting, the researchers crafted their own experiment that used the same premise as the marshmallow experiment. However, the study focused exclusively on adults, unlike the marshmallow experiment, which tracked children into adulthood.

“This was a study of adults of a wide age range (25 to 65), that essentially found that if we test your delay discounting, we can make a pretty good guess about how much money you earn,” said Hampton.

The researchers offered study participants a choice between immediate smaller rewards or larger rewards after a delay period. The participants completed a delay discounting task over Amazon’s Mechanical Turk, a crowdsourcing internet marketplace.

Participants were offered a choice between a smaller sum of money ($500) immediately or a larger sum ($1,000) at five different delay periods of one day, one week, six months and one year.

If a participant chose the delayed reward, the next question was an immediate reward midway between the rejected immediate reward and $1,000. This continued with each passing question until the participants choices converged at a so-called “indifference point.”

A lower indifference point demonstrates a higher reward impulsivity, meaning they had less ability to wait for the reward.

The researchers found that participants with a higher indifference point, and therefore more impulse control, tended to have a higher income.

“We measured delay discounting rate behaviorally by asking people to choose between immediate smaller and delayed larger rewards over a series of trials,” Hampton explained. “This allowed us to hone in on how much people devalue rewards they have to wait for, which relates to more commonly understood things like impulsivity and the ability to delay gratification.

“In this context, higher delay discounting rate is roughly equivalent to higher impulsivity and to lower ability to delay gratification.”

The study only followed adults, but it could nevertheless be informative for parents who would like their children to grow up to be affluent, Hampton pointed out.

“Our study was cross-sectional and therefore our results do not speak to directionality,” he said. “However, there is some evidence that delay discounting is malleable and therefore teachable. If this is the case, then a parent endeavoring to guide their children to a higher income might be wise to instill in their child the importance of foregoing small rewards in favor of larger delayed ones.”

“This is probably easier said than done, as few of us enjoy waiting,” he continued, “but it is possible that children who develop this ability are investing in their own earning potential.”