NEW YORK (Thomson Reuters Foundation) - More than a third of the world’s population, or 2.6 billion people, live in nations and territories gripped by repression, corruption and human rights abuses, with the worst being Syria, Tibet and Somalia, an advocacy group said on Wednesday.

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The year 2015 - shaped by mass migration, crackdowns on dissent, xenophobia and terror attacks - marked the 10th straight year of decline in global freedom, according to an annual report by the Washington-based Freedom House.

Worldwide, 86 nations and territories were designated free based on their political rights and civil liberties, 50 were deemed not free, and 59 were partly free, it said.

The bulk of those deemed unfree were in the Middle East and North Africa, where 85 percent of the population lives with repression; sub-Saharan Africa where 20 regimes earned the not free ranking; and Eurasia, where no country was listed as free.

The report singled out the United States - while free - as slipping, citing “a disturbing increase in the role of private money in election campaigns,” legislative gridlock, a lack of openness in government, racial discrimination and a dysfunctional criminal justice system.

Freedom declined in 72 countries in 2015, the most since the 10-year slide began.

There were gains in 43 countries, with upward trends in Burkina Faso, Myanmar, Nigeria and Sri Lanka, which all held elections.

The slowdown in the Chinese economy and lower commodity prices took a toll, said Arch Puddington, vice president for research at Freedom House and co-author of the report.

“In many countries with authoritarian governments, the drop in revenues from falling commodity prices led dictators to redouble political repression at home and lash out at perceived foreign enemies,” Puddington said in a statement.

“Democratic countries came under strain from terrorist attacks and unprecedented numbers of refugees - problems emanating from regional conflicts such as the Syrian civil war.”

Notable for the year was a lack of progress for women, the report said.

Citing Saudi Arabian women participating in elections and an end to adultery as a crime in South Korea, it said: “The very limited steps that were hailed as victories... demonstrated just how low the bar has gotten in evaluating progress toward gender equality.”

Rounding out the dozen nations and territories with the worst scores were North Korea, Uzbekistan, Eritrea, Turkmenistan, Western Sahara, Sudan, Central African Republic, Equatorial Guinea and Saudi Arabia.