How accurate is geo ip data on the U.S. state level?

Question

We would like to implement slightly different behavior in our web application for those who visit from a certain state (Florida) vs. those in the rest of country (and world).

It's not critical that it be 100% accurate but well into the 90s-- it's OK if a few Floridians see the other version, and others see the Florida version.

What is your experience with state-level identification of users based on their IP address?

Yes I understand the theoretic limitations of using this information (ISPs, proxy servers, yada yada), but I don't know how this plays out in the real world. There are some great answers about the different providers and accuracy, but they don't really answer our state-level empirical question. Google provides some, but not the information we're looking for.

Thanks. We don't want to pursue this approach if it won't work good enough.

Answer 1

MaxMind, which offers a popular IP-to-location database published some statistics on its data:

• GeoIP City Accuracy for Selected Countries

This is the data they published for USA (last updated May 17th, 2010):

• Correctly Resolved Within 25 Miles of True Location: 83% (85%)

• Incorrectly Resolved More Than 25 Miles From True Location: 14%

• Not Covered on a City Level: 3%

Definitions:

• Correctly Resolved Within 25 Miles of True Location: refers to the IP addresses that are correctly resolved within 25 miles of the actual city. The second number in parenthesis refers to the percentage of IP addresses that are correctly resolved if excluding data not covered on a city level.

• Incorrectly Resolved More Than 25 Miles From True Location: refers to IP addresses that were incorrectly resolved by more than 25 miles of the actual city.

• Not Covered on a City Level: refers to the percentage of the data of select country that does not contain city information. We leave these data ranges without city information to prevent false positives. The city information is not available for AOL IP address or when Internet Service Providers (ISPs) route traffic through proxies thus masking the originating location.