The underlying drivers for property ratings are the dividends (net operating income) and capital gains over a certain holding period, and their associated risks or variances.
Similar to other financial ratings developed for mutual funds and stocks, it can be assumed that investors have constant relative risk aversion over the wealth derived from other sources and from their investments.
Adam Smith wrote in The Wealth of Nations over 200 years ago that "a dwelling-house, as such, contributes nothing to the revenue of its inhabitants".
Add on top attributes that span markets, housing, government, community, demographic and lifestyle parameters.
A sound rating analysis should cover all aspects of location – national, state, metro, county, city, tracts down to neighborhoods and the property itself.