In an age of expanding national security powers, increasing surveillance state, and rolled-back civil liberties protections, Americans' perception of their own personal freedoms is plummeting, according to the annual ranking by the Legatum Institute in London.

In Washington D.C. this week to promote their findings, researchers with the Legatum Institute measure a nation's prosperity on a number of factors including health, safety, education, economy, opportunity, social capital, governance and personal freedoms.

According to the 2014 Index (pdf) released earlier this month, in the measure of personal freedom, the United States has fallen from 9th place in 2010 to 21st worldwide—behind such countries as Canada, the United Kingdom, Germany, Uruguay and Costa Rica.

The scores are based on 2013 polling data provided by Gallup, which questioned citizens' satisfaction with the nation's handling of civil liberties, freedom of choice, tolerance of ethnic minorities, and tolerance of immigrants.

According to the Legatum researchers, "evidence suggests that the greater the level of freedom in society the greater the satisfaction with life." However, they note that of the types of freedom tested for, "economic freedom is most important for life satisfaction and wellbeing across a range of countries."