Ground crew members hold a Japanese flag as they wave to a Japan Maritime Self-Defense Force's P3C patrol plane as it leaves the Royal Malaysian Air Force base for Australia to join a search and rescue operation for the missing Malaysia Airlines, flight MH370, in Subang, Malaysia, Sunday, March 23, 2014. Search planes headed back out to a desolate patch of the southern Indian Ocean on Sunday in hopes of finding answers to the fate of the missing Malaysia Airlines jet, after China released a satellite image showing a large object floating in the search zone. (AP Photo/Lai Seng Sin)

According to data recently released by the Organization for Co-operation and Development (OECD), more than half of Russian adults held tertiary degrees in 2012 -- the equivalent of college degree in the United States -- more than in any other country reviewed. Meanwhile, less than 4% of Chinese adults had tertiary qualifications in 2012, less than in any other country. 24/7 Wall St. reviewed the 10 countries with the highest proportion of adults holding a college degree.

The most educated populations tend to be in countries where tertiary education spending is among the highest. Tertiary education spending in six of the most educated countries was higher than the OECD average of $13,957. Spending on tertiary education in the U.S., for example, was $26,021 per student, by far the most in the world.

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According to Andreas Schleicher, director for education skills at the OECD, education in the U.S. has become much more expensive, and student debt burdens have reached troubling levels in recent years. Despite these facts, it is still considered a good investment, as U.S. residents with higher degrees earn substantially more than their less educated peers.

It is also a worthwhile investment for the government. Schleicher explained that “taxpayers in the U.S. get $200,000 more out of every graduate than what they actually invested, so it’s a good business for the government as well.”

Despite the value of investing in education, there are exceptions. Korea and the Russian Federation both spent less than $10,000 on tertiary education per student in 2011, considerably lower than the OECD average. Yet, they still have among the most educated populations.

Qualifications do not always translate into stronger skills. While only 1 in 4 of U.S. college graduates reach the top-end of literacy skill, more than 35% reach that level in Finland, Japan, and the Netherlands. As Schleicher explained, “We typically describe people by their formal qualifications, but this data suggests that the skill value of formal qualifications vary considerably across countries.”

Nevertheless, countries with strong higher education systems tend to have higher levels of advanced skills. Roughly 12% of adults across the OECD performed at the highest literacy proficiency level in 2012. The percentage of adults performing at the highest literacy level exceeded that figure in five of the most educated countries.

Those higher skills may be paying off for residents. Only Ireland had an unemployment rate higher than the OECD rate of 7.5% in 2012. According to Schleicher, this relationship may also work the other way around because those who are employed are far more likely to pursue higher education and training. Unfortunately, this means “those who need life-long learning the most actually get the least out of it.”

To identify the most educated countries in the world, 24/7 Wall St. reviewed the 10 countries with the highest proportions of residents aged 25 to 64 with a tertiary education in 2012. These data were included as part of the OECD’s 2014 Education at a Glance report. The countries considered included the 34 OECD member countries, and ten non-OECD nations. Included in the report were data on the proportion of adults completing various levels of education, unemployment rates, as well as public and private education expenditure. We also reviewed data from the OECD’s Survey of Adult Skills, which included advanced adult proficiency in both math and reading. The most current figures for education expenditure by country are from 2011.

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These are the most educated countries in the world.

10) Ireland

> Pct. population with tertiary education: 39.7%

> Average annual growth rate (2005-2012): 5.2% (4th highest)

> Tertiary education spending per student: $16,095 (12th highest)

Nearly 40% of Irish adults between the ages of 25 and 64 had tertiary qualifications in 2012, the 10th highest rate among all countries reviewed by the OECD. This represents a substantial increase from more than a decade ago when just 21.6% of adults had completed some form of higher education. Worsening employment opportunities in recent years may have made higher education more attractive to the country's residents. More than 13% of the population was unemployed in 2012, one of the highest rates among countries reviewed. The unemployment rate for college-educated adults, however, was considerably lower. Pursuing higher education is especially attractive for citizens of European Union countries because their tuition is heavily subsidized at public institutions in Ireland.

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