You're 25% figure is highly questionable. As you surely noticed when you got that number from Trulia, average rent in SM actually decreased from $4800 to $4600

You're 25% figure is highly questionable. As you surely noticed when you got that number from Trulia, average rent in SM actually decreased from $4800 to $4600 between July 2015 and January 2016. You would need to see numbers going back more than 12 months to come up with a meaningful estimate. Your 5% figure is based on a model purpose-built for San Francisco. In particular the number for elasticity of demand is likely wrong for Santa Monica. Considering how sensitive the model is to this parameter, it seems pretty iffy to present 5% as a meaningful estimate of anything.