Just 54% of U.S. student-loan borrowers are making consistent payments, instead alternating between months of larger payments or no payment at all, according to a study from the JPMorgan Chase Institute that underscores the burden of educational expenses for millions of Americans.

Among borrowers who started making payments, as many as 59% might be making no payment at any given time, the institute said in a report released Wednesday in Washington. The payment status changes reflect income swings, and show families are less consistent paying student loans than those for cars and homes.

Outstanding student-loan balances have more than doubled in the past decade to about $1.5 trillion held by almost a fifth of the population, Federal Reserve Bank of New York data show. The new study of those obligations is based on checking-account customer data from more than 4 million families who paid student loans between 2012 and 2018, according to the institute, part of JPMorgan Chase & Co.

Though the typical family paid 5.5% of take-home income toward student loans in months where a payment was made, the financial burden weighs the most on young and low-income households, according to the report by institute President Diana Farrell, a former economic adviser to President Barack Obama, and fellow researchers Fiona Greig and Erica Deadman. The institute’s goal is to use the biggest U.S. bank’s customer data to help policy makers and businesses better understand the economy and make more informed decisions.

The institute found that one in four borrowers under 25 spends 16.8% or more of take-home pay on student loans, while households making $50,000 or less spent 14.7% or more. By income group, 44% of low-income families made consistent loan payments versus 63% for high-income families.

Account holders ages 25-34 typically pay $121 a month across all months. A quarter pay an average of $340 each month a payment is made. Paying $340 a month would cover a home-loan equivalent of more than $70,000, assuming a 30-year mortgage with an interest rate of 4.12%, the latest national average according to the Mortgage Bankers Association.

“Our aspiration is to ensure that the conversation shifts,” Farrell said in an interview. “Even though some progress has been made on this regard, the burden for young households and low-income households is still way too high.”

The share of the population with student loans has held at about 18% since 2016, up from 10% in 2004, according to a New York Fed report in May. “The prevalence of student loans grew steadily between 2004 and 2016, with very rapid growth in both participation and balances seen during the depths of the Great Recession, when college enrollment increased,” researchers wrote.

--With assistance from Alex Tanzi.

This article was provided by Bloomberg News.