Excerpt from this article:
Jetpac is a clever app that analyzes Instagram photos to create city guides. By identifying markers like how much lipstick people are wearing, or the number of mustaches showing, it rates places as, say, “bars women love” or “hipster hangouts” (a mustache indicating hipsterism in some cities).
Now, Jetpac has turned its technology to happiness. Crunching through 150 million images, and awarding “smile scores” based on the incidence and strength of smiling, it gives us a ranking of the world’s happiest places. You may be surprised by the results.