Comparing annual median home prices to partial year prices is not really an apples-to-apples comparison because of the effect of market seasonality on sales prices - and year to date, some cities are up, some down and some are basically unchanged. It's hard to discern a definitive trend.
We chose the selection of cities below because they had higher numbers of sales than other communities, while representing a range of price points. Still, in the first 5 months of 2019, Tiburon only had 26 house sales reported to MLS, a surprisingly low number. (Belvedere and Ross had even fewer, but they never have many sales.) Full-year 2019 median home prices may be significantly different than the year-to-date figures.