One of the few natural advantages of New York City has always been that Manhattan is an island, meaning that a gunshot fired in Harlem might be heard on the Upper West Side, where dwell people who have the clout to get a city councilman on the telephone and be taken seriously when they demand that something be done about it. That advantage persists in a diminished state, but other related advantages do not. The most important of New York’s was that the city long enjoyed a kind of monopoly status as a place that certain kinds of people simply had to be in order to conduct business: If you were in finance, you needed to be near Wall Street. If you were in publishing, media, or fashion, you needed a presence in Manhattan, which gave your employees a strong incentive to want to be there, too. That is no longer as true as it once was, and that is a problem for Bill de Blasio and his central campaign promise, which was, if you have forgotten, a very large transfer of wealth from New York City’s private sector to its public sector. His tax-the-rich program overlooks that an ever-dwindling number of high-income people and firms have a strong financial attachment to New York. You meet a lot more hedge-fund guys in Dallas these days than you used to. The headquarters of a fair number of Manhattan-based financial firms already have over the years followed their employees to Connecticut or beyond.

The super-rich may or may not mind that much — especially given that their income tends to come in the form of capital gains, which receive preferential tax treatment — but your $100,000-a-year midlevel workers already have discovered the roads to Charlotte and Salt Lake City. And as Mike Bloomberg was lambasted for pointing out, you can’t ignore the super-rich, either, given that fewer than 100,000 New Yorkers pay half the city’s taxes, and 500 of them pay 15 percent of the city’s taxes. That is problematic in and of itself, but it’s not like everybody else gets off the hook — de Blasio’s tax hike on those who make $500,000 or more will have real consequences for people in less rarified income brackets. When your landlord, vendors, or customers get a tax hike, their problems have a way of becoming your problems, which is why a fair number of people who will never have incomes approaching that cutoff point understand that they will nonetheless be affected by it. That and a great deal of skepticism about de Blasio’s commitment to sustaining Mayor Giuliani’s crime policies have a fair number of New Yorkers across the income spectrum rethinking their leases.