“According to a recent survey by the National Association of Realtors, in fact, 25 percent of all buyers financed 100 percent of the purchase price, and 42 percent of first-time home buyers bought with no money down.” link
This is nationwide data, and I know the figures are much higher in San Diego. After all, the prices are much higher here. Did you know that 25% of all loan in Wyoming are adjustable? Now why would people in Wyoming need to get into such a loan while we have the lowest interest rates in decades?
Keep in mind this is a survey done at purchase, and not updated when those same buyers refinance or take on a HELOC.