Without an intimate knowledge of the communities that will allow you to calibrate properly, you are going to be just as accurate taking the random numbers generated by Zillow and Trulia.
Now, be advised, there are many enterprises (Bank of America) who will actually use Zillow as a basis for evaluation of the value of a house. If you want to be considered as competent as Bank of America, then the tax assessed value, Zestimates. Evaluations and the gray beard at the end of the street are all legitimate sources.
If, however, you are on the verge of making a real estate decision, you would be well advised to rely on the knowledge and experience of those who help in the sale and purchase of dozens of homes every year. They are just a phone call away.
Best of Success,
Annette Lawrence, Broker/Associate
Palm Harbor, FL
Take a look at the "Market In A Minute" (MIAM) reports I've posted on Trulia. The data revealed are the indicators regarding whether the tax assessed value has any relevant relationship to market value. But, with a MIAM report, you have all the data you need anyway.
Hope that helps,
1. About half of the time, assessment was higher than purchase price, about half the time lower.
2. Nearly half of the time, the difference was drastic (greater than 10 percent).
3. The most extreme differences were in cases where the purchase price was much lower than the assessment value.
Based on my very limited data set, it seems that assessment value is slightly less effective than, say, the Zillow estimates as a predictor of sale value (though it is a good predictor of what you will pay in taxes).
You can do a similar check for your town (using online tools like trulia, redfin, zillow, eppraisal, etc.)
And take it all with a grain of salt. For many purposes (say, determining which neighborhoods are pricier than others), crude ballpark figures are enough --- but when you're deciding how much to offer for a home, you probably shouldn't be happy with an estimate that leads you to overpay by 20% a good fraction of the time.
If your question is about negotiation psychology (e.g., you want to give a lowball offer legitimacy by pointing out to the seller that you are, after all, offering the assessment price), then you should also add that you believe that a more careful CMA supports the assessment value (if this is indeed the case). But in the end, your ability to get the home at a lower price will depend on the seller's motivations and on how much interest other people are showing in the house at the current listing price. (Are there already three offers near or above the listing price? Or are there no offers --- with the house sitting around for months, sometimes going entire weeks without a single showing?) This is information that the seller has and you don't (though the listing agent may be willing to give you hints, if it is in the seller's best interest to do so) --- and it has little to do with assessment value.
To determine the best asking or offer price, you need to rate the specific property with SIMILAR properties.
You can't compare the sale/assessed value of a 4 bedroom, new construction colonial with that of a 2 bedroom, 20 year old ranch. Have a market analysis done and make sure who ever is doing it is comparing apples to apples.
I am a certified residential appraiser as well as a real estate agent. Assessments are based on historic data, and with the volatility almost ALL markets in MA have experienced lately, it is nearly impossible to base market value on assessed values. As RealtyMan states the very best you can hope for is to determine a ballpark ratio of assessments to selling prices. Your best bet is to have your agent do a thorough market analysis, or get an official appraisal done, in order to help you determine a reasonable offer.
The only way to know for sure is to compare the sale prices of recent sales to the current assessment. If you are lucky, you'll determine a ratio. It's a guide but by no means should it replace a thorough market analysis on the specific property.