Couples who shack up before tying the knot are more likely to get divorced than their counterparts who don't move in together until marriage, a new study suggests. Upwards of 70 percent of U.S. couples are cohabiting these days before marrying, the researchers estimate. The study, published in the February issue of the Journal of Family Psychology, indicates that such move-ins might not be wise. And it's not because you start to get on one another's nerves. Rather, the researchers figure the sha