Lindismith,
It’s 23% of single family homes and 28% when you look at both single family and condos combined.
PS,
The national numbers are irrlevant as prices are cheaper in other places and speculation much higher. All the stats you point out in SD are areas where speculation far exceeded the mean in SD. Downtown and cheap condo conversion were full of speculation and are the exception. I saw a report for SD (cant remember exactly where) but they put the number of investors/2nd home buyers at 18% in SD overall.