It's an age-old question: If you had to choose between more time and more money, what would it be?

Researchers at the University of Pennsylvania and University of California Los Angeles wanted to find out in a study they published in the journal Social Psychological and Personality Science.

Here's what they found:

People who value time over money are happier

The scientists ran several studies — online surveys, in-person surveys, nationally representative surveys of more than 4,000 people — asking the same basic question: What would you rather have, more time or more money? The surveys also contained questions on personal well-being.

Most people were practical: Around 64 percent surveyed answered "more money."

But there was something else: The people who said they'd prefer more time were generally happier.

What's more, this relationship held true when the researchers controlled for the participants' time and money.

It's not that people who have more money are happier and have more freedom to say they'd want more time. It's much more subtle than that. "What matters is the value people place on each resource," the authors write. "Beyond the amount of these resources people have, happiness is linked to the resource people want."

It's important to note, however, that there were some differences between the people who chose money and those who chose time. And the authors note these differences warrant further study.

People who tended to choose more time also tended to be:

Older, which suggests perhaps as we age we get more satisfaction from valuing our time over money

Parents, which suggests children can change our values on the time-money question

Married

Wealthier (but when the analysis controlled for this, the correlation between choosing time and happiness remained)

Money and time are both often scarce. It can be genuinely frustrating to decide which matters more.

People want both more time and more money, the researchers from UCLA and the Wharton School write, "but unfortunately there is rarely an opportunity to simultaneously gain in both."

Life is a series of trade-offs between the resources. The researchers list some common examples:

Should you pay more for the direct flight that gets you to your destination sooner? Should you accept the higher paying job that requires more hours in the office? Should you take on the huge financial burden of receiving the best medical care available for the possibility of extending your life several years?

All these questions — and more — are complicated when relationships enter the equation: Should we spend more time with our kids or work harder to provide for them?

There probably isn't any research that can definitively answer these questions. They're too thorny, too broad to apply to the messy lives of individuals. But this latest paper does lend some insight.

For many, this isn't even a practical choice

It's a gift to be able to even consider choosing between time and money. For many — people who work multiple jobs, at odd hours, scraping by to feed their family — there's never enough of either. But as the paper persuasively shows, even if you know money is more important, valuing time could lead you to a happier life.

As far as whether more money would make us all happier, there's actually conflicting evidence. A famous 2010 paper found that happiness and wealth are correlated up until an income level of around $75,000. But a subsequent 2013 paper out of Brookings found the opposite. Looking at international data, Brookings reported, "If there is a satiation point [meaning the point at which money stops correlating with happiness], we are yet to reach it."

Overall, how we use our time might be slightly more in our control than how much money we earn. And how we value that time is absolutely in our control.

Money can come and go. Time only goes.