Sampling error for subgroups may be higher. It's easy to get married in the United States. All it takes is a license and a trip to the marriage bureau. Divorce court has become as much a part of the American scene as health food stores, or baseball diamonds, or college campuses. As a country, we have the highest divorce rate in the world.
Marriage laws are the oldest laws in existence.
The first were carved in stone in the marketplaces of Babylon by King Hammurabi thousands of years ago. Each society makes marriage laws that favor its needs. In a society that needs soldiers, the marriage laws favor the production of male children. In a society based on property, the marriage laws are engineered to protect property. In a society where women are regarded as possessions, the marriage laws reflect that.