Judging from personal experience, you may have an inkling that housing prices seem to be on the rise. You may have heard anecdotes that many families can’t even buy a home due to increasing costs and lack of availability, forcing them to remain renters instead. After all, anywhere from 20% to 40% of all households live in rental housing units. But even finding an affordable place to rent is becoming a real challenge for many, as is evidenced by this year’s Harvard Joint Center State of the Nation’s Housing Report.

The report is celebrating its 30th anniversary this year. Since it was first released in 1988, more than 40 million housing units have been built throughout the U.S., with the nation adding 27 million new households. But these days, fewer families are owning their homes — and fewer families can afford their rent.

In 1990, approximately 38.9% of renters spent more than 30% of their income, while 19.3% of those renters gave more than half their income right over to their landlord. But in 2016, 47% of households who rent in the U.S. — which equates to 20.8 million families — spent more than 30% of their income on rent. What’s more, 25.2% (or 11 million households) spent half their income on rental housing.

It’s clear that the costs of renting the average apartment have grown much faster than the average American’s take-home pay. According to the Joint Center, of rental households that earn less than $30,000 per year, 80% are cost-burdened — meaning they have to use more than 30% of their income to pay for rent. Making matters worse, the report reveals that new housing is in low supply. That, in turn, has an adverse effect on affordability. Although there were 1.2 million new housing starts in 2017, the total increase from the previous year was attributed to single-family residences.

Unsurprisingly, that means renters are now remaining in their existing homes for longer periods than they did in the past. Although statistics show that 33% of renters move each year, many are choosing to stay put due to a lack of more affordable options. While those who live in luxury apartments can have their pick of available units, those who need more affordable housing don’t have that choice — highlighting the disparity between the haves and the have-nots.

In the report, Harvard Joint Center for Housing Studies managing director Chris Herbert noted: “We need strategies to help the private sector produce more moderately-priced housing… [This] will require new approaches for making effective use of public funding, reducing construction costs and easing regulatory barriers.”