Concerns over privacy and “Big Brother” type government surveillance have grown exponentially in the last few years, matching the growth of social media and the mobile internet. Most people are at least somewhat concerned by the idea that the government is monitoring what we do on Twitter.

The ambitiously named Expert Labs, a non-profit startup that focuses on social media crowdsourcing, aims to turn the tables, in a manner of speaking. Yesterday they introduced the Federal Social Media Index, a tool that indexes and analyzes the Twitter activity of 125 government agencies in order to determine which agency does the best job of interaction with the public via the social media platform.

Although the index was introduced yesterday, it has data covering the last three weeks of November. The index tracks the various agencies’ Twitter usage and ranks them according to their engagement with their followers. Top rankings go to the account with the most replies from followers overall (the State Department), the one with the most answered question overall (the Marine Corps), and the one with the most answered question by percentage of followers (the US Mint).

The index is fully automated, powered by Expert Labs’ ThinkUp software, a tool for tracking and analyzing an organization’s social media output. The stated goal of the index is to help disparate government agencies to learn from one another’s use of social media – to see what works best for each agency, in hopes of improving every agency’s interaction with its followers.

The index also includes a sortable chart containing the entire list of tracked agencies. The chart can be organized by number of followers (NASA is at the top with 1.3 million), number of questions asked by the agency (National Endowment for the Arts), number of questions answered by followers (the Marine Corps), and best question-to-answer ratio (the US Mint). Each agency on the index also has its own profile that provides more detail about its activities on Twitter.