Dual-career commuter couples  Commuter couples are a subset of dual-career couples who live apart in separate residences while both partners pursue careers. Gilbert and Rachlin address the difference between dual-earner families and dual-career families, distinguishing that dual-earner couples are those in which both spouses are earning for the family, but one or both of them consider their occupational involvement as a job. Jobs are unlike careers in that they do not require extensive training or commitment. In dual-earner couples, one spouse's work is generally considered secondary. Dual-career couples are families in which "both heads of household pursue careers and at the same time maintain a family life together". Both have high degrees of commitment to their careers, and neither partner's career is thought to be more important than that of the other. In the United States, statistics from as early as 1989 report that 53% of married households were dual-earner couples. By 1996, the percent of dual-earner couples grew to 61%. According to data from 1989, approximately 7 million employees (15% to 20% of all dual-earner marriages) were classified as dual-career couples. By 2003, U.S. workers take more than 400 million long-distance business trips (i.e., trips over 50 miles) each year. Commuter marriages are on the rise, with recent estimates indicating that as many as 3 million Americans reside in different locations from their spouses. The increase in women's career opportunities also increases the problems of couples pursuing two careers in the same place, and can cause conflict regarding which spouse's career should take precedence. One major concern for dual-career couples is finding employment in the same geographic location. One partner usually compromises by taking a less desirable job so that the other can take a position that might further his or her career. However, if this compromise cannot be reached, the option of commuting can be the result, where both spouses enjoy highly desirable jobs at the sacrifice of maintaining separate residences. In the definition of dual-career commuter couples, the work pursued by each member of the couple requires 1) a high degree of commitment and special training with increasing degrees of responsibility (this includes students pursuing an advanced educational degree) and 2) that the couple maintain homes in separate geographic locations. Traveling sales or business workers, military personnel, migrant workers, and construction and trade workers who leave home for various lengths of time are not included in the definition. When couples share a home and one or both members commute long distances to work each day or couples immigrating at separate times, they are also not included in this definition.