The article doesn't mention anything about age. Age predicts happiness[1] as well as walking speed. I suspect it predicts economic performance, although I don't

The article doesn't mention anything about age. Age predicts happiness[1] as well as walking speed. I suspect it predicts economic performance, although I don't have any references. It's certainly common for young people to migrate to large cities with strong economies to find work [2]. Were there controls for the average age of residents? The original paper[3] doesn't mention controls or age at all. This seems like a major issue to me. 1. http://www.euro.centre.org/data/1207216181_14636.pdf http://www.euro.centre.org/data/1207216181_14636.pdf 2. Interactive US map here: http://www.netmigration.wisc.edu/ http://www.netmigration.wisc.edu/ 3. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.389.6823&rep=rep1&type=pdf http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.389...