Employees unionize to obtain outcomes that they believe they are unable to obtain as individuals. Member desires have a major impact on union bargaining goals. It has been suggested that contract demands reflect the preferences of the "median voter" in a unit,' thus requiring that the con tract be acceptable to at least a majority to be ratified. Local union officers are often elected by a single bargaining unit. Bargaining success directly influences their ability to be reelected. Where local unions service several bargaining units, local officers might be less concerned about the content of individual contracts Unions demonstrate their effectiveness by negotiating contracts that improve employment conditions for their members, attract new members, and organize additional units. As an institution, the union desires security as the employees' representative through negotiated union shop agreements. Two major goals of unions are higher wages and more members.13 Labor is presumed to prefer both, but in dealing with employers, unions often make trade-offs between them. If wages increase relative to competitors, an employer must reduce employment (membership). For wages to increase, productivity must grow at least at the same rate. However, a national union might be willing to sacrifice a small fraction of employment in a unit to gain higher wages that will increase its organizing leverage in nonunion units with increasingly lower relative wages.