A worker cooperative or producer cooperative is a cooperative that is owned and democratically controlled by its "worker-owners". There are no outside owners in a "pure" workers' cooperative, only the workers own shares of the business, though hybrid forms exist in which consumers, community members or capitalist investors also own some shares. In practice, control by worker-owners may be exercised through individual, collective or majority ownership by the workforce, or the retention of individual, collective or majority voting rights (exercised on a one-member one-vote basis). A worker cooperative, therefore, has the characteristic that the majority of its workforce owns shares, and the majority of shares are owned by the workforce. Membership is not always compulsory for employees, but generally only employees can become members either directly (as shareholders) or indirectly through membership of a trust that owns the company.