When did New York City really shutdown? It's a critical question for anticipating when the epidemic in the city may peak. The city's subways are both a vector for contagion and perhaps the best metric of its activity and mobility. Here's the data. talkingpointsmemo.com/edblog/when-di… 
2/ As you can see, the first week of March was business as usual, even a speck above avg on some days. Week two decline significantly but still largely business as usual. It was only in week 3, after the schools closed when the city really started to wind down.
3/ But it was only on the last day of the third week that subway ridership fell below 25%.
