A national survey shows that about 62.4 percent of couples who were questioned said they were happy with their marriage, and \"loving and respecting each other.\" And it found that Chinese couples considered loyalty the most important virtue in maintaining a good marriage. About 69.4 percent of couples said the least tolerable mistake was having extramarital affairs. About 67.8 percent of husbands and 70.4 percent of wives thought so, the report said. In more developed east China, 65.1 percent said they had a good relationship with their spouses. The ratio was 63.5 percent in central China and 57.9 percent in the less developed western region. The survey, released yesterday by the All-China Women\'s Federation, covered 9,645 couples in 10 provinces, municipalities and autonomous regions between October last year and April. The average age of those who took part was 41 and 70 percent were aged from 31 to 50. About 64.5 percent of the couples said they were \"satisfied\" or \"very much satisfied\" with their sex life. The more the husbands and wives were educated, the happier they seemed to be with their sex life, according to the survey. Only 7.5 percent of husbands and wives who never went to school felt satisfied with their sex lives. The ratio increased to 28.6 percent among those with a bachelor degree or higher. According to the survey, about 70.2 percent of couples were happy or very happy with their lives. Happiness was strongly related to the couples\' perception of their economic status, the survey report said.