Mention should be made of the narrow notion of national income used by U.S. economists. In a narrower sense, national income is calculated as NNP minus all indirect taxes (excise taxes, taxes on cigarettes, gasoline and all other sales taxes). However, it should be borne in mind that all personal direct taxes, as well as taxes on corporate income, are included in the national income. If the NNP can be called “a net national product calculated in market prices,” then this variant of national income can be defined as “a net national product calculated not at market prices, but at factorial costs of production (excluding indirect taxes).”