The richest 1 percent have got significantly wealthier in most countries over the past three decades, with the most speculator rise seen in the U.S., according to a new report by the Organization for Economic Co-Operation and Development (OECD).
The research group found that the richest 1 percent's share of U.S. income had more than doubled since 1980, nearing 20 percent in 2012. This trumped the share of income held by the wealthy in other English-speaking countries such as Australia, Canada, Ireland and the United Kingdom.
The OECD report, published on Wednesday, was part of a study into income equality undertaken over the last few years. The organization used the figures to call for reforms to the global tax system, joining a number of top-earners who have called for more equitable regimes, including Pimco's Bill Gross, Berkshire Hathaway boss Warren Buffett and former Microsoft chief Bill Gates.
The OECD highlighted that the top personal income tax rate in developed countries has fallen to an average of 43 percent in 2013, from 66 percent in 1981.
"This reduction has been closely associated with rising top income shares," it said in the report.
The OECD also noted that corporate taxes had favored the top percentile.
"Without concerted policy action, the gap between the rich and poor is likely to grow even wider in the years ahead," OECD Secretary-General Angel Gurría said in the associated news release. "Therefore, it is all the more important to ensure that top earners contribute their fair share of taxes".
Commenting on the data, Jonathan Portes, director of the U.K.'s National Institute of Economic and Social Research, noted thi particularly high levels of income inequality in the U.S. and U.K.
"The increase has been significantly less, to significantly lower levels in a number of countries, suggesting that while part of this is about general trends, it is not inevitable and country-specific factors and policy can make a difference," he said via email.
The report observed that high earners gained a bigger slice of the income pie over the last 30 years even in countries with a greater tradition of income redistribution. For instance, in Finland, Norway and Sweden, the top 1 percent's share of national income increased by 70 percent to between 7 and 8 percent. However, top earners saw their share grow much less in some other European countries, including France, the Netherlands and Spain.
The main focus of the report was how high earners in developed countries had been affected by the global financial crisis of 2008. The OECD reported that while their incomes fell "significantly" during the first few years of recession, they were quick to bounce back.
"In 2010, top incomes had already started to recover in many countries. On average, real incomes of the top 1 percent increased by 4 percent in 2010, while the lower 90 percent of the population saw their real incomes stagnate," it said. "Financial crises seem to have no clear-cut permanent effect on top incomes."
This tallied with findings from Emmanuel Saez, a professor of economics at the University of California, Berkeley. Using data from tax filings, he found that the share of the U.S. wealth held by the country's top 1 percent was back to pre-Wall Street Crash levels. Saez noted that since the crisis of 2008, the top 1 percent of incomes had grown by 31.4 percent, while the bottom 99 percent of incomes has grown only by 0.4 percent.
Follow us on Twitter: @CNBCWorld