Palo Alto, the beeping, whirring heart of Silicon Valley, has a homelessness problem. Even as the upscale city has become home to billionaires like Mark Zuckerberg and Larry Page, nearby families sleep in vehicles and garages, and one-third of area schoolkids are homeless.

But Palo Alto has another problem. Its more fortunate residents live next to empty and unused homes. These locals pick up the mail and move recycling bins for their nonexistent neighbors, they say, and regret the “social hole” left by their nearly year-round absence.

Rows of abandoned homes are meant to be a trait of poverty-stricken cities like Detroit or Flint. Why are they plaguing wealthy neighborhoods in the heart of Silicon Valley?