[UPDATE BELOW] Taxi customers have been able to pay by credit card since 2007, and occasional reports since then have indicated that the 20-30% default percentages for tips has led to an increase in the average tip, from less than 15% in the pre-credit days to almost 20% now. We decided to dig into the data* and see what it said.

First, it's clear more people are paying with credit cards— just in the last four years, the percentage of trips paid by card has shot up from around 20% to just under 50%:

But as more people have paid with credit cards, the average tip has declined. Despite 20% being the lowest default option, New Yorkers are still paying less than that, around 17.6% at the end of 2012:

One explanation is that a good percentage of people are still keying in the old lower rates— perhaps 10% or 15% one each ride. [Another explanation, from Boris in the comments below, is that some people tip 0% and pay whatever they prefer in cash.] Another interesting trend: in 2009 and 2010, the tipping percentage shot up over the summer, maybe because of tourists flooding the city over vacation season. But the last two years that trend seems to have vanished— has the Great Recession changed the way tourists tip?

*N.B.: we got the data from the Taxi and Livery Cab Commission through a Freedom of Information Act Request. We've made it public here.

UPDATE: TLC Commissioner David Yassky rang in to dispute the notion that New Yorkers have become cheaper tippers. In fact, he says, a detailed analysis of the graph does not indicate a decline in rates. He argues that pre-2011, the higher volatility in the graph is due to a smaller number of customers paying by credit card, and if you average across this volatile period, the average tip was still about 18%.

He also has an intriguing argument for the decline on the right side of the graph, after the recent fare hike in September 2012: "most people don't use the default tip calculators— this shocked me when I learned this... most people enter their own tip amount. They ignore the defaults, and enter a round number- $2, $3, $5 dollars, depending on the fare. So they are still putting in a $2 or $4 tip amount, but the fare has gone up. The average fare used to be $12.50 and now it's $14. So the size of the tip hasn't changed, but the percentage of the fare has gone down because the fare size changed. New Yorkers are tipping the same nominal amount, but it's a smaller percentage of the fare."

So there you have it: New Yorkers haven't gotten cheaper— they've just failed to adjust their nominal tipping amounts to keep up with the rising taxi rates. After some extended cogitation, we've provisionally accepted this explanation and changed the headline of this story accordingly.