The estimates, based on numbers available till three months ended June this year, are for a grouping of 33 nations including the United States and Spain.
The Organisation for Economic Cooperation and Development (OECD) is an umbrella entity of 34 countries. The latest estimates exclude Chile.
According to data compiled by OECD, one in three of the unemployed people in the member nations have been out of work for more than 12 months at the end of June quarter.
"That represents nearly 17 million people, nearly double the number of long-term unemployed in Q4 2007, then around 8.6 million," the grouping has said.
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Since the start of global financial crisis, which worsened in 2008, unemployment numbers have been on the rise as corporates trimmed workforce to save costs. Also, the pace of generation of new jobs have come down.
Among the member nations, Iceland and the United States have seen the biggest rise in long-term unemployment.
Long term unemployment refers to being out of work for over 12 months.
Other countries with high levels of long-term unemployment include and Slovak Republic (70.7 per cent), Greece (65.5 per cent), Ireland (59 per cent), Italy (56.4 per cent), Portugal (56.1 per cent), Slovenia (49.6 per cent), Spain (49.3 per cent) and Estonia (48.5 per cent).