(CN) – Homeless encampments and “tent cities” have exploded across the country the past decade – growing by more than 1,000 percent – according to a report released this week by the National Law Center on Homelessness & Poverty.

The 124-page study conducted by the legal advocacy group, aimed at ending and preventing homelessness, found encampments and other makeshift shelters increased by 1,342 percent between 2007 and 2017, with two-thirds of the growth happening after the Great Recession was declared over.

Advocates counted only homeless encampments reported by the media in the last decade, since many encampments are hidden or frequently moved and evade being documented during official homeless counts by government and nonprofit agencies. Only 19 encampments were covered in media reports in 2007, compared to 274 reported encampments in 2016, according to the report. As of mid-2017, there were 255 encampments reported nationwide.

The report comes amid an unprecedented housing crisis across the nation, led by states like California which has both failed to build enough units to keep up with demand and has also lost thousands of affordable housing units which have turned market rate.

California had the highest number of encampments, according to the study, though encampments were found in every state. Half of media reports which documented the number of people living in encampments found more than half of them had 11-50 residents, and 17 percent of encampments had over 100 residents, according to the report. Many of the encampments have become semi-permanent fixtures in their cities.

Eric Tars, a senior attorney at the law center and the lead researcher on the report, said in an interview encampments have exploded post-recession in the wealthiest nation in the world due to 40 years of “underinvestment” in affordable housing. He noted since the late 1970s the U.S. Department of Housing and Urban Development’s budget has been slashed in half.

“It used to represent a real safety net for people that would catch the elderly, people with disabilities, people who couldn’t work or people who were working but were poor,” Tars said.

“There was a basic commitment that we shouldn’t let our fellow Americans go homeless, but in the 1980s that commitment fell apart. In the 1980s we saw the emergence of modern homelessness.”

Tars said what was lost in federal funding subsidies for affordable housing wasn’t made up at the state or local level. Now, a third of California renters spend 50 percent or more of their income on rent, putting them one missed paycheck or medical emergency away from becoming homeless.

Only a quarter of renters eligible to receive federal housing subsidies actually receive them, Tars said.

The foreclosure crisis exacerbated shortages in the affordable housing supply when former homeowners entered the rental market and further “squeezed” those at the bottom, Tars said.

While advocates know that “housing first” policies work best at eliminating homelessness, Tars said advocates support sanctioned homeless encampments like one in Las Cruces, New Mexico, since it will “optimistically” take at least a few years to replenish the affordable housing supply and people need places to stay in the interim.

San Diego tested the waters with sanctioned homeless camps this fall, when it opened a city-owned parking lot to more than 200 people in hopes of quelling a hepatitis A outbreak that has killed 20 people and hospitalized hundreds. The city also opened parking lots for people living in their cars.

Tars said legalized encampments reduce fears that homeless people are taking over city streets, which the attorney said often results in cities responding to homelessness with punitive law enforcement policies, such as encroachment laws used to ticket people living on city streets and parking laws used to ticket and impound the vehicles people live in.

While the report finds cities like San Diego and Denver have responded to encampments through criminalization, other cities are integrating legalized encampments as a way to help address homelessness and provide stability for people and their belongings to help them get off the street more quickly.