Nine days ago, in an effort to slow the spread of the coronavirus, Gov. Andrew Cuomo asked New Yorkers to avoid crowds and any kind of “density.” The day before, transit riders had logged more than 5 million trips on New York City subways, with more than a half a million of those subway trips beginning or ending at Grand Central or Penn Station. Cuomo suggested that, if a train car was crowded, riders simply wait for the next one. But, given the heavy usage of the subways, it was immediately clear that effective social distancing would require many fewer people to ride the subways.

To reduce commute-related crowding, Cuomo and New York City Mayor Bill de Blasio also asked New Yorkers to start working from home and change their shifts to avoid rush hour. Columbia University had canceled in-person classes by Monday, with many other colleges shutting down or going fully online later in the week. Private employers, such as Google, Baker McKenzie, and, yes, Slate, have all shut down offices and told employees to work from home.

How well did this work? As it turns out, this past week offered a great experiment in how well voluntary social distancing, led by universities and private employers responding to government asking politely, works in practice. And trip data that the MTA shares publicly offers some early answers. Looking at turnstile entries for the past week, trips were down 33 percent on Friday, as compared with the previous Friday. Here’s the overall picture:

Every station, with the possible exception of West Farms Square (which is next to a bus depot in the Bronx), saw ridership declines by Friday.

Columbia was the first university in New York City to cancel classes. Not surprisingly, therefore, the station with the single largest drop in entries was 116th St. - Columbia University, which fell by 62 percent by the end of the week.

The major transit hubs, where the subway connects to suburban commuter rails, were also down about 41 percent overall, with Grand Central down 48 percent.

And finally, a number of stations on the 1 line, from the World Trade Center up through 23rd Street, were down more than 50 percent, perhaps due to employers along the West Side, such as Google, shuttering their Chelsea offices.

As impressive as voluntary measures reducing ridership by one-third in a single week is, that level of reduction in ridership is not enough to stop the spread of the coronavirus. This week, the city will begin mandatory shutdowns of schools, restaurants, and bars to slow transmission. Last week, we saw the kinds of reductions asking nicely can bring; this week, we will see what full-throated government restrictions can do.