Bill- I agree with James....you can not look at Bergen County with a wide angle lense. Instead, decide what towns or markets you prefer, and then work with a realtor to research where the list to sell price ratio is. In fact, use Ridgewood as an example where how homes performance from list to sell varies by the section of town. How much of a reduction a home took in the Country Club section will differ greatly than in the Lawns.
This number is also affected greatly by how a home stands against its competition in quality, and most importantly how close to market value the home was listed at when it was first listed