Wage increases for Koreans in their 20s and 30s have lagged behind the growth in salaries earned by older workers for the fifth consecutive quarter.

Statistics Korea on Wednesday said the average monthly salary of households of more than two people led by a breadwinner in his or her 30s stood at W4.08 million (US$1=W1,064) in the third quarter of 2012, up only 2.7 percent compared to the same period a year earlier. That was only one-third of the wage increase among Koreans in their 40s and 50s over the same period.

Households led by those in their 40s earned W4.68 million on average, up 7.4 percent, and W4.62 million for those in their 50s, up 8.4 percent.

The main reason behind the virtual standstill in income among younger households appears to be the job market, according to Lee Jun-hyup at the Hyundai Economic Research Institute. "It is becoming increasingly difficult for young people to find jobs, so there is a high chance that the gap between age groups will grow," he said.

An increasing number of older women who join the workforce are also having an effect. Employment among women in their 50s rose close to 6 percent from 51.8 percent in 2003 to 57.7 percent in 2011, but among women in their 20s it grew a mere 1.4 percent to 58.7 percent over the same period.