The U.S. may have the world's largest economy, but it does not even crack the top 10 percent when it comes to a perceived lack of corruption.
That is just one of the findings in the 18th annual Corruption Perceptions Index released Wednesday by Transparency International, a global non-profit organization dedicated to fighting corruption.
The U.S. ranked 19th out of 176 countries in this year's index, scoring 74 on a scale of zero to 100, where zero is "highly corrupt" and 100 is "very clean." Transparency International says it scores each country using multiple sources of data on perceived corruption in the public sector.
(See the complete rankings at www.transparency.org)
"Corruption is the world's most talked about problem," said Transparency International Managing Director Cobus de Swardt in a statement. "The world's leading economies should lead by example, making sure that their institutions are fully transparent and their leaders are held accountable."
Among the countries with scores higher than the United States are Hong Kong, which ranks 14th with a score of 77, Germany at 13th with a score of 79, and Canada and the Netherlands which tie for 9th place with a score of 84.
Denmark, Finland and New Zealand tied for the "cleanest" country this year, each scoring 90 in the index.
(Read More: 10 Corruption Hot Spots)
There is also a three-way tie for the most corrupt country, between Somalia, North Korea and Afghanistan, which scored just eight points each.
"In these countries, the lack of accountable leadership and effective public institutions underscore the need to take a much stronger stance against corruption," Transparency International said.
Transparency International, which has been issuing its corruption rankings since 1995, said it has updated its methodology this year. That, and the fact that the study ranks just 176 countries in 2012 versus 183 in 2011, makes year-to-year comparisons difficult.
Nonetheless, the data suggest worsening corruption in some countries in turmoil. For example, Greece fell to 94th place in 2012 from 80th last year. Egypt ranks 118th in 2012, compared to 112th in 2011. Italy drops three places to 72nd.
Transparency International says it has consistently warned euro zone countries to deal with corruption as they tackle a financial crisis.
Despite a long history of pronouncements about corruption and a major crackdown after 9/11 attack, the U.S. has never been a stellar performer in the rankings. Last year, it recorded its worst finish ever at 24th.
New Zealand, Denmark and Finland, by contrast, have consistently finished at or near the top. New Zealand finished first last year, followed closely by Denmark and Finland in a tie for second place. Last year's most corrupt countries were Somalia and North Korea.
Two countries profiled earlier this year in the CNBC Investigations Inc. documentary Filthy Rich remain among the more corrupt in the world, according to Transparency International.
(Read More: Greed Keeps Public Corruption, Bribery Alive)
The former Soviet Republic of Azerbaijan, which is home to abundant oil reserves and a key network of pipelines, ranks 139th with a score of 27—a slight improvement from last year's 143rd place finish. The country has been the subject of international scrutiny over the business dealings of President Ilham Aliyev's family.
Oil-rich Equatorial Guinea has also been the subject of international scrutiny, with the governments of the U.S. and France attempting to seize property linked to President Teodoro Obiang Nguema Mbasago—the longest serving head of state in Africa—and his son, Minister of Forestry Teodoro Nguema Obiang Mangue. Equatorial Guinea improved to 163rd place in this year's rankings, from 172nd in 2011.
Watch an encore presentation of "Filthy Rich" Thursday, Dec. 6 at 8:00 p.m. ET on CNBC.
—By CNBC's Scott Cohn; Follow him on Twitter: @ScottCohnCNBC