When it comes to making money, consistency may be almost as important as quantity.

Families that had large fluctuations in their incomes — even when it was a 25% gain — were more likely than those with stable incomes to say they wouldn’t be able to come up with $2,000 for an unexpected need, according to a study by the Philadelphia-based nonprofit Pew Charitable Trusts released this week. The study looked at “income volatility” among more than 5,600 families the term for a year-over-year change in annual income of 25% or more, between 2014 and 2015.

“Volatility in general, regardless of the direction, is very disruptive to families,” said Erin Currier, the director of Pew’s financial security and mobility project, who called that volatility “a roller coaster” for many Americans. “It makes it harder for them to plan.”

More than a third of those households surveyed experienced these large changes in their incomes from 2014 to 2015, Pew found. That number has been fairly consistent over time, Currier said. Households of various incomes see major dips and drops, but since volatility is measured as a percentage change in income, those with lower incomes had the lowest threshold for qualifying as having volatile incomes, Pew’s report says.

In fact, there were more households in the years Pew studied that saw a gain in their incomes than those who saw dips, which is probably less surprising given that the economy was growing in those years and many families were finally getting back on their feet after the Great Recession.

Roller coaster finances are more common than many people realize. A quarter of people saw their incomes rise or drop by 30% or more, according to an analysis of 27 million Chase bank accounts between 2013 and 2014 by the J.P. Morgan Chase Institute JPM, -1.14% , a J.P. Morgan Chase think tank. Those fluctuations were about the same, regardless of account holders’ incomes. One problem: Although income and spending both change, they don’t always change in the same direction, which can create budgeting problems. Put bluntly, some people keep spending even when they and their families experience a reversal of fortune.

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Pew did not specifically ask what the families’ professions were who reported these large fluctuations. But those dips and hikes happen for a variety of reasons, from changing to a job with a significantly higher salary to one spouse leaving the workforce or getting laid off unexpectedly, or a divorce leading to a separation of finances. It also could be that a sudden hike is merely offsetting a major dip the previous year, Currier said.

Financial technology, including mobile applications that automate savings, could be one way to make short-term saving easier, Pew’s report says. (There are many applications that do this, and some even allow users to set parameters including setting aside money from larger-than-average paychecks.)

Employers who can give employees advance notice of how many hours they’ll be working would obviously help; paying employees more frequently than just every two weeks can also help lower income families budget, given that some struggling households turn to high-interest loans, including payday loans, Pew found. Perhaps unsurprisingly, just one third of Americans write out a budget at all. The issue, Currier said, “clearly needs more attention and possibly intervention.”