Anyone trying to understand the wild fluctuations in Belmont’s median home price need look no further than this chart.

We’ve tracked the median home price in Belmont over the last year—ever since the mortgage crises. What we were looking for was the impact it would have on home values. We sure were stunned to see a $200,000 median price increase last December, which lead us to go back and track the median size home selling too; this way, we could adjust for larger or smaller homes selling in a particular month.

Now that we’ve plotted the data, it’s easy to see that the dramatic swings in median value correspond directly to the large fluctuations in the size of the homes sold during a particular month.

Belmont only has 20 or so sales a month—sometimes far less—so just a few larger than average homes selling can really skew the true median price.

(click on the graph for a larger view)

Data retreived from the Multiple Listing Service–ProListing of San Mateo County