Quick: What is the biggest reason that one in four American workers says it's becoming harder to maintain a decent work-life balance?

Could it be that clients are demanding more face time? That old-school bosses are resistant to telecommuting? Or that new technology means you're never really "away" from work?

Nope. It's that wages aren't growing.

That's according to a new survey from Ernst & Young, which looks at the efforts of about 9,700 employees in eight countries to maintain a work-life balance. Of about 1,200 U.S. workers who were queried, about a quarter said it was becoming harder for them to have a healthy work-life balance. And the number-one reason, according to a full half of respondents, was "My salary has not increased much, but my expenses have."

The second-place answer, chosen by 43 percent, was "My responsibilities at work have increased." And both of them beat out, by significant margins, "I don't have the ability to work flexibly at my current job," which was cited by only 16 percent of respondents.

The top answer--wage stagnation--looks like a nod to what is euphemistically called "help." "Help" is what enables many working parents to maintain a semblance of sanity; it's one aspect of leaning in that Sheryl Sandberg has been criticized for failing to fully address. "Help" does not refer to neighbors rushing over with trays of lasagna at any hint of crisis; we're talking about nannies, housekeepers, gardeners, and even private chefs, none of whom typically work for free.

"As much as we say that time is money, it's equally true that money can be time," says Scott Behson, a professor of management at Fairleigh Dickinson University, and the author of the upcoming The Working Dad's Survival Guide. "If you're going to be working longer hours, but you have a little more discretionary income to have help cleaning the house or getting good or going on vacation, money certainly does help."

Behson also notes that as companies emerge from the recent recession, many have adopted a new normal in which employees are essentially asked to do more with less, work longer hours, and take on more responsibility. But they haven't necessarily been paid more for doing that. "That sets up a dynamic where people feel unfairly compensated," says Behson.

Pay, unlike flexibility, is easily measured. "People are working more hours, and pay is something that is extremely visible," says Karyn Twaronite, global diversity and inclusiveness officer with Ernst & Young. "So workers can clearly measure whether or not that's stagnant or advancing, the same way they can measure promotions."

That makes it easy to get dissatisfied with pay, especially for those new to the labor markets. "Younger workers would look at a high-level woman and say, 'It's easy for you to be successful and have children because you're more senior. You can afford all the backup childcare options, you can outsource more. It's much harder for me,'" says Twaronite.

There are other economic factors bearing down on younger workers, too, says Twaronite: The ability to buy a house and having student debt were both factors these workers are taking into account when deciding whether or not to have children, according to the study.

Both Twaronite and Behson say that maintaining a decent work-life balance isn't a matter of money or flexible scheduling and other perks--they should both be part of a more cohesive, holistic compensation package. And they offer advice for those who are currently struggling.

Twaronite says communication is key. Yes, employees should continue to raise their hands for challenging assignments that will help their careers--and then make sure to spread the word when they knock the ball out of the park.

"Share your accomplishments, and take credit for where you've gone above and beyond, so you continue to build on your reputation and capital," she says. "When needed, you can cash that in for extra flexibility." That helps establish a results-oriented dynamic, where getting the work done is more important than face-time.

Behson sounds like he'd like to hear less apologizing. "If you need to leave early one day for whatever reason, as long as you're a good employee, just go," he says. "You don't need to advertise that it's for family, but you don't need to hide it, either." A recent study found that men are more likely to do this--and to essentially fake an 80-hour work week--while women are more likely to ask permission.

Last, he says, we need to remember that work-life doesn't always have to be work versus life. "One's career can be a very important part of a full life."