One solution, suggests professor Michael Moses of New York University’s Stern School of Business, is to apply real estate valuation techniques to art. Moses developed the MEI Moses All Art Index, which uses auction sales information to track the ups and downs of art investments. Art collectors and investors can use the benchmark’s underlying database, available to subscribers at artasanasset.com, to find recent prices for works comparable to pieces they’re considering. The database lets you compare art according to type, size, artist, and previous sale prices.

This approach ought to be familiar to any homeowner. When you buy or sell a house, you and your agent use recent sales of comparable properties to come up with a reasonable price to ask or offer. These “comps” look at square footage, location, numbers of rooms and bathrooms, and other factors. With art, says Moses, the trick is to find truly comparable works, and the more similarities, the better. If you can locate a recently sold painting, for example, that is of a similar size and was done by the same artist in the same style as a work you want to buy or sell, you’ll have a good idea of what might be a reasonable price.

Moses notes that off-category and smaller pieces tend to fetch lower prices. So if you come across a small portrait by an artist who normally paints large landscapes, the portrait may be considerably less valuable than one of the landscapes would be. To determine how much lower the price should be, look for other smaller portraits by this or a similar artist.

Because prices from much earlier sales may not say much about current value, artasanasset.com includes a “market to market” feature that helps you gauge how much a piece may have appreciated. But Moses cautions art buyers and sellers not to consider art comps as the last word on a work’s value. Instead, they provide a starting point for an auction sale or for negotiating with a gallery or private collector. The ultimate price depends on demand and perceived value. Like beauty, a work of art’s value is in the eye of the beholder.