A recent study shows that an unequal share of household chores is still the norm in many households, despite the fact that many more women now have jobs. In a survey of 1,256 people ages between 18 and 65, men said they contributed an average of 37% of the total housework, while the women estimated their share to be nearly double that, at 70%. This ratio was not affected by whether the woman was working or not.

When they were asked what they thought was a fair division of labour, women with jobs felt that housework should be shared equally between male and female partners. Women who did not work outside the home were satisfied to perform 80% - the majority of the household work - if their husbands did remainder. Research has shown that, if levels increase beyond these percentages, women become unhappy and anxious, and feel they are unimportant.

After marriage, a woman is reported to increase her household workload by 14 hours per week, but for men the amount is just 90 minutes. So the division of labour becomes unbalanced, as a man's share increases much less than the woman's. It is the inequality and loss of respect, not the actual number of hours, which leads to anxiety and depression. The research describes housework as thankless and unfulfilling. Activities included in the study were cooking, cleaning, shopping, doing laundry, washing up and childcare. Women who have jobs report that they feel overworked by these chores in addition to their professional duties. In contrast, full-time homemakers frequently anticipate going back to work when the children grow up. Distress for this group is caused by losing the teamwork in the marriage.

The phrase "two decades" in line 1 refers to a period of _______. A. 10 years B. 20 years C. 50 years D. 100 years