The world’s richest 1 percent owns more wealth than economists had thought, depriving countries of billions of dollars in tax revenue and revealing an even bigger income gap shift in global inequality.

New research by European Central Bank economist Philip Vermeulen and London School of Economics economist Gabriel Zucman, conducted separately, shows the ultra-wealthy’s money, often hidden in tax shelters, is undercounted. World Bank research shows that correcting income data nearly erases the progress made from 1988 to 2008 in narrowing the gap between the world’s rich and poor.

Economists estimate wealth with various government surveys of households, but the surveys often have small sample sizes, and the rich respond less to surveys than the poor do, hiding the wealth of the nonresponding households, Vermuelen wrote in a July paper. He readjusted data, supplemented it with “rich lists” like the Forbes World’s Billionaires list, and found that the 1 percent held 35 to 37 percent of global wealth in 2010, whereas the U.S. Federal Reserve’s Survey of Consumer Finances reported the portion at 34 percent.

The heavy concentration of wealth at the top of economies could explain the slow recovery from recession in consumer spending, Joseph Stiglitz, the Nobel Prize-winning economist and author of "The Price of Inequality," told Bloomberg.

The amount Americans spent on discretionary services like travel agencies and dining out nosedived during the recession in 2009, and though it has picked up, it remains well below a pre-recession peak and is growing slower relative to other periods of economic growth. The slow growth in consumer spending that’s occurring seems to be coming more from upper-income earners than middle- and lower-income earners.

From 2009 to 2012, income for the top 1 percent of earners grew by 31.4 percent, while everyone else’s incomes rose an average 0.4 percent, according to an analysis by UC Berkeley’s Emmanuel Saez and the Paris School of Economics’ Thomas Piketty.

Over the past 18 months, Bloomberg’s Mass Merchant Index, which measures profit of businesses like Wal-Mart Stores Inc. (NYSE:WMT) and Dollar General (NYSE:DG), rose 80 percent, while the Standard & Poor’s index of the top 500 companies rose 109 percent over the same period. Meanwhile, luxury retailers like Coach Inc. (NYSE:COH) and Prada S.p.A. (HKG:1913) have gained 254 percent, according to Bloomberg’s Global Luxury Goods Index.

That could help explain why middle- and lower-income Americans are reporting less confidence in the economy than upper-income Americans.

Accurate measurements of the world’s wealth would help economists and governments craft tax policies to reduce fraud and illegal tax evasion.

Globally, 8 percent of the world’s personal financial wealth is held offshore, costing more than $200 billion to governments annually, and despite policy initiatives, corporate and personal profit shifting to tax havens and offshore wealth are rising, Zucman wrote. She argues for an international financial registry that would make avoiding taxes by taking advantage of overseas banking rules more difficult.