The median home sales price in the San Francisco Bay area plummeted 47% in the past four years, hitting $351,500 in December, compared to $665,000 in the middle of 2007, DataQuick said. The steep drop shows how far prices have fallen in a metro area where sellers used to record high profits by offloading real estate. DataQuick attributes half of the peak-to-trough drop to declining home values, while the rest is tied to a shift in the sales mix. The area saw 7,494 home sales in December, DataQuick said. That is up 18.6% from 6,317 sales in November and 4.4% higher than 7,178 last year. Distressed homes now make up a considerable amount of sales in the nine-county central California region. Foreclosure resales and short sales represented 49.6% of the December resale market, up from 45.9% in November and 48.2% last year. Higher-priced homes attracted fewer buyers in December, with the number of homes selling for above $500,000 falling 5.7%. Homes selling for less than $300,000 increased 15.2%. Write to Kerri Panchuk.