BLOG — Nov 01, 2021
US Monthly GDP Index for September 2021
By Ben Herzon and William Magee
Monthly GDP rose 0.2% in September following 1.0% growth in August (unrevised). The increase in September reflected increases in domestic final sales and nonfarm inventory investment that were partially offset by a decrease in net exports. About one-half of the increase in domestic final sales was accounted for by personal consumption expenditures.
The level of GDP in September was 1.9% above the third-quarter average at an annual rate. Implicit in our latest forecast of 4.9% (annualized) GDP growth in the fourth quarter are increases in monthly GDP averaging 0.3% per month (not annualized) over the three months of the fourth quarter.
Our index of Monthly US GDP (MGDP) is a monthly indicator of real aggregate output that is conceptually consistent with real Gross Domestic Product (GDP) in the National Income and Product Accounts. The Monthly GDP Index is consistent with the NIPAs for two reasons: first, MGDP is calculated using much of the same underlying monthly source data that is used in the calculation of GDP. Second, the method of aggregation to arrive at MGDP is similar to that for official GDP. Growth of MGDP at the monthly frequency is determined primarily by movements in the underlying monthly source data, and growth of MGDP at the quarterly frequency is nearly identical to growth of real GDP.