If you are just looking at the Market Trends graph for one town or community be sure to look at the graph below it that indicates the number of transactions. In only Marblehead, there is a relatively small number of sales that go into the data on the grid. I do not believe there is a deep decline in the market. Without further investigation, I would guess the decline in the graph is something as simple as the more recent sales are inferior homes to the ones sold 3-12 months ago. When there is a small set of data any number of things can skew the graph. Hope this helps.
Brian Shifrin, Esq.
Attorney & Counselor
Certified Real Estate Appraiser