In the United States, unionization rates have historically been lesser in relations to several European countries. The U.S. adheres to the principle of "employment at will," meaning that companies can terminate workers with or without cause, and workers can abandon their positions without notice. Collective bargaining is common in unionized work environments, where labor unions negotiate with companies on behalf of union members. Collective bargaining habitually focusses on wages, benefits, working conditions, and job security