One reason for the stabilizations of divorce is the reduction in the risk factors—fewer teenagers marrying, fewer early births in marriage, fewer pre-marital(婚前的) conceptions.
Another reason which was aired at the annual conference of the British Society for Population Studies, was the increase in cohabitation. Some speakers argued that the increase in cohabitation has meant that marital couples are now much more familiar with each other before marriage and therefore less likely to separate.
One out of four couples who marry today have lived together and in the older age groups the proportion is much higher. Some 34 percent of women aged over 25 who marry have cohabited, and over 50 percent of women who are marrying a divorced man or who have been divorced themselves, cohabit before marriage.
Cohabitation in Britain, however, is still considerably lower than in many European states and was described by the demographers as "essentially a part of contemporary courtship". Only a small proportion of people who cohabited had children whereas in Sweden some 40 percent of births were now outside formal marriage. The British rate was 13 percent.
Kath Kiernan of the Centre for Population Studies noted that the present statistics suggested that there was a marginally higher risk of separation for couples who had cohabited, but this could possibly be explained by the fact that the statistics covered a period when cohabiting had not become as socially acceptable as it was today.
A third reason why the demographers thought the divorce rate could stabilize was the economic squeeze(利润等的缩减) and the recession(暴跌), which would mean there was less opportunity to separate because of the lack of housing and employment.
The phrase "levelled off" (Para. 1) most probably means ______.

A. increased
B. decreased
C. fluctuated
D. became stable