WASHINGTON — With 2013 bringing tax increases on the incomes of a small sliver of the richest Americans, the country’s top earners now face a heavier tax burden than at any time since Jimmy Carter was president.

The last-minute deal struck by the departing 112th Congress raised taxes on a handful of the highest-earning Americans, with about 99.3 percent of households experiencing no change in their income taxes. But the Tax Policy Center estimates that the average family in the top 1 percent will pay a federal tax rate of more than 36 percent this year, up from 28 percent in 2008. That is the highest rate since 1979, at least.

By some measures, the tax code might now be the most progressive in a generation, tax economists said, while noting that every American is paying a lower burden currently than they did then. In fact, the total federal tax rate is still vastly lower for the very rich than it was at any point in the 1940s through 1970s. It has risen from historical lows, but is still closer to those lows than where it was in the postwar decades.

“We made the system more progressive by raising rates at the top and leaving them for everyone else,” said Roberton Williams of the Tax Policy Center, a research group based in Washington. “The offsetting issue is that the rich have gotten a lot richer.”