As we all know, Facebook lets people update their friends with status updates, and with millions of users, that’s a lot of data. Look at the aggregated data over time, and you could see some interesting trends.
The Facebook Data Team recently measured happiness in the United States based on these updates with a metric they call United States Gross National Happiness.
Measuring how well-off, happy or satisfied with life the citizens of a nation are is part of the Gross National Happiness movement. This graph represents how “happy” the nation is doing from day to day, by looking at how many positive and negative words people are using when they update their status: When people are using more positive words (or fewer negative words) in their status updates than usual, that day is happier than usual!
(via Facebook Measures Happiness in Status Updates | FlowingData)