Bah, stick to the truth: 20 years is for the decent but super cheap apartments, if you pay “market rates” you can get something from the private owners within months.
I admit that I pulled the 20 years stats out of a hat. I quickly looked for some stats, and this page suggests around 10 years average for the private market, and 13 years for the communal: https://www.stockholmdirekt.se/nyheter/sa-lange-maste-du-koa...
An article on the current situation: https://www.theguardian.com/world/2015/aug/19/why-stockholm-...