In discussing the possibility of legalizing ADU's in Honolulu, someone commented that the Santa Cruz ADU graph looked great, but what happened after 2007 -- the year the Great Recession started to really take hold?
To recap, here's the ADU graph comparing the # of building permits issued for ADU's.
The # of ADU's created per year seems to follow the same downward trend as the # of new single-family dwellings created each year. Since ADU's are smaller or involvle conversions of existing space, their construction costs are less and thus, as expected, even when there were no new single-family dwellings permitted in 2009, Santa Cruz still had 2 new ADU units.
References:
http://cityofsantacruz.com/Modules/ShowDocument.aspx?documentid=20602 Scroll allllll the way down to the end: Appendix F, to see the data.