Two weeks ago, my wife and I visited Portland, Oregon. I had not been in Portland since photographing there two years early, while working on “Homeless in a Land of Plenty.” There seem to be hundreds more unsheltered persons sleeping Portland’s sidewalks and its open open spaces than there were just two years ago.

According to statistics available from the City of Portland, an average of 2,000 people sleep unsheltered each night. Sadly, homelessness is on the rise, not just in Portland, but across the country.

And why is homelessness on the rise? The top 20 percent of housing consumers in America make an average of $155,000 a year. Collectively, 19 percent of this group’s income goes toward housing. In stark contrast, the bottom 20 percent make an average of just over $10,000 a year, and spend on average 89 percent of their income on housing. On any given night, more than 550,000 American experience homelessness. Among comfortably housed Americans, there are those who struggle with alcoholism, substance use issues, mental health challenges, and/or who have made a poor decision or two in their lives.

These afflictions and challenges are not the cause of homelessness. Homelessness will remain one of our most pressing social problems, unless and until we make significant and sustained investments in affordable housing.