In most states, workers' compensation laws have been devised to provide coverage and protection to as many employees as possible. For that reason, most states require most employers to obtain adequate insurance coverage, and to provide workers' compensation coverage to all of their employees. However, there are a few key exceptions to this rule of thumb. Some states may offer workers' compensation exemptions to employers and employees in a number of specific categories. For example, some very small businesses or sole proprietorships may not be required to offer workers' compensation coverage. In addition, some casual part-time positions may not be covered, and household domestics such as maids and yard workers with part-time schedules are usually exempt. On the other hand, large companies with significant annual revenues may not be required to carry workers' compensation insurance with a third-party carrier. Instead, these companies agree to cover their own workers' compensation claims and costs, and are considered to be "self-insured" rather than technically exempt.