About 20% of Opus Dei are celibate. They live in special residential centers where they lead extremely structured lives— critics say this practice isolates its members from the rest of society and allows Opus Dei to have nearly total control over its members' environments. For some books, a numerary's direct supervisor can provide permission, but for other books, permission can only be given by the prelate in Rome. According to some critics, Opus Dei pressures numeraries to cut off social contact with non-members, including their own families. Numeraries in Opus Dei generally hand over their entire salaries to the organization, and critics say this makes numeraries extremely dependent upon the organization.