Paying taxes is rarely pleasant, but as April 15 approaches it’s worth remembering that our tax system is a progressive one and serves a little-noticed but crucial purpose: It mitigates some of the worst consequences of income inequality.

If any of us, as individuals, are unfortunate enough to have income drop significantly, the tax on that income will plummet as well — and a direct payment, or negative tax, might even be received from the government, thanks to the earned-income tax credit. In this way, the tax system can be viewed as a colossal insurance system, guarding against extreme income inequality. There are similar provisions in other countries.

But it’s also clear that while income inequality would be much worse without our current tax system, what we have isn’t nearly enough. It’s time — past time, actually — to tweak the system so that it can respond effectively if income inequality becomes more extreme.

I made this argument in 2003 in my book “The New Financial Order” (Princeton University Press). And now there is substantial evidence that inequality has been rising rapidly. In his monumental new book, “Capital in the 21st Century” (Belknap Press), Thomas Piketty of the Paris School of Economics documents a sharp increase in such inequality over the last 25 years, not only in the United States, but also in Canada, Britain, Australia, New Zealand, China, India, Indonesia and South Africa, with people with the highest incomes far outstripping the rest of society. The book is impressive in its wealth of information but it is short on solutions.