According to Wikipedia SF City and County has a population of 870k, Warsaw 1.8 million. The metro area 4.6M vs 3.1M respectively. So I'd say the same ballpark. That said 5000 units seems like nothing at these population sizes. I live near Wrocław (650k city population, 1.1M metro), there were 10.000 new units in 2016 and this year will be similar. And this number doesn't include private investments (people building a house for themselves), only housing built by developers and sold on the market.