Click to enlarge. (Data source: Edelman survey, 2013)

Just under half of adults in 18 of the world's most important economies say they trust banking institutions "to do the right thing," according to a new study by the public relations firm Edelman. The study found that percentage dropped from 56 percent in 2008 to 45 percent this year.

The above map shows how those numbers break down among the 18 countries surveyed. To be clear, these are not the world's largest economies: Indonesia and Australia are not included, in favor of European bellwethers Ireland and Sweden. The data are part of Edelman's annual "trust barometer" survey, which attempts to measure public trust in large institutions.

You might immediately notice a few apparent trends here. The most-trusted banks are in India and China, where an estimated 80 and 83 percent of people say they trust them. China's banking system is very tightly controlled by the state – so tightly that many Chinese actually use unofficial, illegal "shadow banking" networks for borrowing and lending.

Trust is by far the lowest in Europe, which is maybe no surprise as the Eurozone crisis drags on. And the numbers across Europe have dropped dramatically since 2008. It's worth noting that trust is low in two European Union states that are not members of the Eurozone: Sweden and the United Kingdom. But it's relatively high in Poland, an EU member state, at 44 percent, although Poland also experienced a sharp decline in trust over the past five years.

What's interesting is that trust in banks seems to line up pretty neatly with economic growth; countries that have more growth also report higher trust in banks. China and India both have rapidly growing gross domestic products. The next most-trusting country, Mexico, reported 3.8 percent GDP growth last year, one of the higher on the list. Canada, Japan and South Korea all experienced moderate GDP growth and have moderate trust in banks. Poland is the most-trusting European country in this survey and also had the highest GDP growth. The clearest exception to this trend is Russia, where GDP growth seems to be outpacing trust in banks; although, given Russia's reputation for corruption, maybe that distrust is not exactly misplaced.

The United States reported 49 percent trust in banks, down dramatically from 69 percent in 2008. Back then, banks were more trusted in the U.S. than in almost any other country surveyed.