The union density or union membership rate is the ratio of the number of employees who are members of trade unions to all the employees in a country or population. This is lower than the collective agreement coverage rate, which refers to all people in work places where terms are collectively agreed. Trade unions collectively bargain with employers for improved pay, conditions, and voice at work by means of the increased bargaining power that employees have together compared to what they would have as individuals. The number of people who are covered by collective agreements is higher than the number of union members, and in many cases substantially higher, because when trade unions make collective agreements they aim to cover everyone at work, even those who have not joined a union. The union density or union membership rate is the ratio of the number of employees who are members of trade unions to all the employees in a country or population. This is lower than the collective agreement coverage rate, which refers to all people in work places where terms are collectively agreed. Trade unions collectively bargain with employers for improved pay, conditions, and voice at work by means of the increased bargaining power that employees have together compared to what they would have as individuals. The number of people who are covered by collective agreements is higher than the number of union members, and in many cases substantially higher, because when trade unions make collective agreements they aim to cover everyone at work, even those who have not joined a union.