The wealth of the top 1 percent grew an average of 3.9 percent a year from 1986 to 2012, though the top one-hundredth of that 1 percent saw its wealth grow about twice as fast. The 16,000 families in that tiptop category — those with fortunes of at least $111 million — have seen their share of national wealth nearly double since 2002, to 11.2 percent.

Image Other forms of luxury transportation also abounded at the annual event — whether a Bentley or a helicopter perched atop one boat. Credit... Andrew Innerarity for The New York Times

“Wealth is getting more concentrated in the United States,” the authors wrote. “But this phenomenon largely owes to the spectacular dynamics of fortunes of dozens and hundreds of million dollars, and much less to the growth in fortunes of a few million dollars.”

Dr. Saez and Dr. Zucman wrote that a “snowballing effect” was creating extravagant wealth at the very top. Outsize incomes — fueled in part by stock — are put into savings and investments, which generate more income, which creates even more wealth.

Mr. Rushton, the jet broker, has seen that snowball up close. During the financial crisis in 2009, the market for virtually all private jets collapsed. Yet, in a contrast to earlier recoveries, the demand for new, large-cabin jets has staged a much stronger comeback while the supply of new and used smaller and midsize jets is piling up.

According a jet market report from Citi Private Bank, deliveries of new so-called light jets — the smaller, cheaper models — were down 17 percent last year from 2012 and 67 percent from their 2008 peak. But deliveries of the biggest new private jets jumped 18 percent last year.

Demand for billionaires’ most coveted jet, the $65 million G650 from Gulfstream, is so strong that some G650 owners are now flipping their planes for millions of dollars in profit just months after buying them. Bernie Ecclestone, the Formula One auto-racing promoter and billionaire, flipped his for about $72 million last fall — just weeks after he received it.

Sales of personal, V.I.P. jetliners are also strong. Boeing has received several orders from individuals for its 777-300ER (which normally carries 400 passengers) and its even bigger 747-800.