Rents in San Francisco continued their upward march in April 2015, according to the just-released Zillow Rent Index. When we last checked in with Zillow's index after the first quarter of the year, it showed rents up 15.5 percent over the same time last year. That number nudged upward in April, with rents now up 16 percent over April 2014 and 1.1 percent over March of this year. If that growth rate continues, San Francisco will easily be on track to hit double-digit rent increases again in 2015. The median rent in San Francisco, according to the index, now sits at a terrifying $4,225/month.

Although growth in San Francisco was huge, growth in Berkeley was much larger, hitting 30.9 percent year over year. Oakland saw 21.6 percent increases over April 2014, Emeryville had a 25.9 percent surge, and Daly City experienced 20.1 percent year-over-year growth in rent. The San Francisco metro area as a whole was up 14.9 percent over the year before, putting its growth level well above any other major city in the United States. Only San Jose, at 12.9 percent, and Denver, at 11.6 percent, came close.

The Zillow Rent Index assesses the rental value of all housing stock, not just what happens to be on the market at any given time, in order to take out fluctuations that may occur by looking just at available inventory at a certain point. It's very difficult to pin down the exact rental median in the city, but Zumper, another rental website that tracks San Francisco rents, showed a 1.8 percent increase in April in the median asking rent for a one-bedroom. (Zumper doesn't calculate an overall median.) No matter what the exact figure is, the one thing that we know for sure is that the rent here is very, very high.

· Rents Gallop Past Home Values in April [Zillow]

· San Francisco Rents Reach an All-Time High, No Sign of Letting Up [Curbed SF]

· San Francisco's Runaway Rents Reach an All-Time High, Again [Curbed SF]