Compact, “micro” apartments might be the next big thing in Seattle’s urban living scene, data from StorageCafe shows.

Seattle is the city with the second-highest percentage of micro-housing units in its rental inventory. Twelve percent of all apartments are smaller than 405 square feet, which is approximately half the size of a typical unit. Some Seattle units are as small as 116 square feet.

In many cities, apartments that small aren’t only rare — they’re illegal to build.

Furthermore, nearly two-thirds of new rentals in Seattle are micro-sized: 66% of all units currently under construction in the city will be, at most, half the size of the average existing apartment.

Space constraints are, of course, part of the reason for micro-housing’s meteoric rise in Seattle and many other West Coast hubs, where land for new development is limited and affordability is low.

The tradeoff for less square footage, though, is a monthly rent nearly half the cost of a conventional Seattle apartment. The average rent for a typical apartment in Seattle is about $2,388 per month. But the average rent for a micro-unit is $1,289.

“Micro-housing is one of the most efficient tools we have to create more housing quickly and affordably, especially in urban areas where land is scarce and demand is high,” said David Nieman, partner at Neiman Taber Architects. “In Seattle, we’ve built about 10,000 micro-housing units over the past decade — renting at rates affordable to people making 40% to 60% of the area median income.”

Neiman said those micro-units play a “critical role in expanding the supply of low-cost, market-rate housing.”

Ultimately, for many renters, like new grads, people who travel frequently for work, recent divorcees or young couples, living small just makes more sense.

“Affordability is clearly a big part of the story,” said Brad Hargreaves, founder and editor-in-chief of Thesis Driven. “There is a segment of renters who simply don’t need as much space and are willing to trade that space for lower rent.”