4% of married women. According to an article by Judith Treas and Deirdre Giesen, cohabiting couples are twice as likely to experience infidelity within the relationship than married couples. Fertility Regarding cohabitation as a fertility factor, a large survey in the United States came to the result that married women had an average of 1.9 children, compared to 1.3 among those cohabiting. The corresponding numbers for men were 1.7 and 1.1, respectively. The difference of 0.6 children for both sexes was expected to decrease to between 0.2 and 0.3 over the lifetime when correcting for the confounder that married people have their children earlier in life. A study of the United States and multiple countries in Europe came to the result that women who continue to cohabit after birth have significantly lower probability of having a second child than married women in all countries except those in Eastern Europe. Another study, on the contrary, came to the result that cohabiting couples in France have equal fertility as married ones. Also, Russians have a higher fertility within cohabitation, while Romanians rather tend to have childless marriages. Survey data from 2003 in Romania came to the result that marriage equalized the total fertility rate among both highly educated and low educated people to approximately 1.4. Among those cohabiting, on the other hand, lower level of education increased fertility rate to 1.7, and a higher level of education decreased it to 0.7. On the other hand, another study came to the result that Romanian women with little education have about equal fertility in marital and cohabiting partnerships. Financial effects In the United States, married couples that submit a combined tax return may face a marriage penalty, where tax credits for low-income single earners are not applied to the combined income. In October 1998, Senate GOP leader Trent Lott decided to pull a bill to abolish "the marriage penalty," "which in the tax code reflects the fact that married couples who both work for wages frequently pay more in taxes than if they earned the same amount of income but weren't married. And the more equal the incomes of the couple, the steeper the marriage tax penalty." The earned income tax credit (EITC) is cash welfare for low-income workers, but the problem is the EITC is not for married couples because they have to combine their wages, which again leads to "the marriage penalty."