Seasonally adjusted flow from BEA, NIPA, Table 3.2, line 4, Taxes on production and imports. Unadjusted flow from BEA, NIPA, Table 3.22, line 4, Taxes on production and imports. Seasonal factors are calculated as the seasonally adjusted flow at an annual rate, divided by four, less the unadjusted quarterly flow. Series has no levels.