A tariff is a tax placed on imported and/or exported goods. The goal is to encourage consumption of domestically produced goods (which do not have the extra cost) and raise revenue. Tariffs are similar to tolls, which have the same kind of effect on the transport of people across borders instead of goods. Tax, tariff and trade rules in modern times are usually set together because of their common impact on industrial policy, investment policy and agricultural policy. A trade bloc generally has no tariffs within its borders but may have very high "tariff barriers" against imported goods or services. There are also non-tariff barriers[?] such as immigration policy.