Government revenues are government income. The main sources of revenue in OECD countries are typically taxes and social contributions, with some income from charges for services provided by the state. In some countries, revenues may include a significant portion from non-tax sources, such as income from state-owned enterprises or royalties on natural resources. Revenue policy is typically designed to serve multiple purposes. The most fundamental is to collect funds to pay for the provision of goods and services for the public, such as health care and defence. Revenue policies will often also be designed not to worsen inequality, such as by levying higher income taxes on those with larger incomes. Revenue policies can also be used to encourage socially beneficial activities (e.g. tax breaks on research and development) and discourage harmful ones (e.g. taxes on carbon emissions or tobacco). In some cases, these different purposes may conflict with each other.