One in every five high-earning, dual-income households has at least one spouse working in the education sector, a think tank report showed Thursday. Based on an analysis of double-income households from government data, the LG Economic Research Institute (LGERI) found that 20.9 percent of household heads in the top income bracket, dominantly men, were married to school teachers, university professors or other education-related job holders as of end-2012. Since 93.4 percent of the nation\'s household heads are men, the finding suggests that 20 percent of female partners in high-earning working couples are teachers. In contrast, only 6.2 percent of the bottom income quintile -- earning a monthly average 890,000 won (US$779) -- had a spouse in the education field. Instead, 10.6 percent of the lowest earning group was married to unskilled laborers, such as office cleaners and call center workers, the report showed. \"Most high-income earners prefer to marry school teachers because teachers get school holidays and have steady income and working conditions,\" said Park Mi-suk, the head of Gayeon Matchmaking Consulting Service, a Seoul-based wedding agency. The research also found a correlation between a couple\'s income and economic participation rate. Fifty-four percent of the spouses of the top income quintile were economically active -- meaning one is either employed or looking for work -- compared with just 16 percent among their low income counterparts. In addition, the former group earned four times as much as the latter. The observed patterns appear to underline the so-called \'assortative marriage\' phenomenon,\" said Ko Ga-young, a researcher at LGERI. According to this cognitive theory, people tend to marry others from similar social, economic and cultural backgrounds because they feel naturally attracted to common traits.