Labor organization affects the formation of relatively separate groups of wage earners both directly and indirectly. First as to its direct influence. A labor union is a combination of a number of individuals, formed with the intention of advancing the material welfare of the group and for such wider purposes as the group may agree upon. The chief peaceful method of unionism is collective bargaining; its chief combative method is the strike. Labor unionism is a factor in the formation of relatively separate groups of wage earners, because each autonomous, or practically autonomous, trade union is a point of pressure upon the distributive mechanism. Each trade union strives to turn the balance of distribution in its own direction. This it does in a variety of ways. It may by its wage demands test out the nature of the demand for the products of its labor. It strives to force the price of these products up to the point which seems to promise the greatest wage income for the group. It may by its pressure on the employer bring about a revision of productive methods. It seeks by its strength to secure that portion of the product which, in its view, goes to the strongest contender for it. Unions, indeed, sometimes strive to restrict the flow of labor into their craft or industry by deliberate regulation or silent obstruction. Such instances are less important than formerly in all probability. On occasion unions may even play a part in determining the field of employment for their members. Thus G. D. H. Cole points out that in England the trade unions do not recognize "differences between skilled and less skilled workers as demarcation disputes, and do not recognize the right of unskilled workers to raise such cases against skilled unions. In fact, the skilled unions virtually claim the right to do such work as they think fit, and so far as they can enforce their claim, to exclude the less skilled where they think fit."[34] Again unionism may indirectly through its wage policy cause a slowing up of recruiting of new men into the craft or industry. In short, by every means at its command, a union strives to assert the importance of its group as against other interests. Thus, in respect to the activities just described, unionism must be included among the influences which lead to the formation and maintenance of relatively separate groups of wage earners.