The income gap between single-income and double-income households for the second quarter this year decreased to the narrowest level since the fourth quarter of 2015, data from Statistics Korea showed Wednesday.

The decline was attributed to lower quality jobs.

Double-income households earned an average of 5.47 million won ($4,830) compared to single-income households’ 3.69 million won.

While the overall number employed in the second quarter increased by over 300,000 from the previous year, the number of those employed in higher-quality manufacturing jobs decreased, as the pay gap between regular and temporary workers increased.