The nation’s income gap appears to have widened, touching off concerns over a further thinning of the middle-income bracket, according to data from Statistics Korea on Thursday.

The state-run Statistics Korea recently announced a research report on national income distribution calculated using the Wolfson Index, which is a barometer for income level of middle-income earners.

The index climbed from 0.254 in 2011 to 0.256 in 2012. The Wolfson Index is a common measure of inequality in which a number closer to zero represents a high ratio of those in the middle-income bracket while a figure closer to 1 indicates severe disparity in the wake of the “collapse” of the bracket.

Statistics Korea officials downplayed the figure for 2012, saying the income gap has recently narrowed after peaking to a serious point several years ago. They cited the figure of 0.264 in 2008 and 0.265 in 2009, when the global financial crisis dealt a blow to the country.

A global research report, however, showed that Korea is one of the few countries that experienced growing income inequality between 1990 and 2010.

The study, entitled “Rising Inequality in Asia and Policy Implications,” released in February, is based on the countries’ Gini coefficient between 1990 and 2010.

The Gini coefficient is a common measure of inequality in which a number closer to zero represents less-severe income inequality while a score of 100 implies total polarization.

According to the study, the Gini coefficient in Korea rose from 24.5 to 28.9 at an average annual pace of 0.9 percentage points during the period, meaning that the country’s income disparity worsened at the fifth-highest rate in the region.

China saw the greatest increase in inequality during the period, followed by Indonesia and Laos. Between 1990 and 2010, the Gini coefficient leaped from 32 to 43 in China, at an average annual pace of 1.6 percentage points, it said.

By Kim Yon-se (kys@heraldcorp.com)