Monthly GDP rose 0.3% in September following a 0.1% decline in August that was revised lower by 0.1 percentage point. The increase in September was more than accounted for by domestic final sales, reflecting gains in consumption and nonresidential fixed investment. Net exports were little changed in September, and nonfarm inventory investment declined. The level of GDP in September was 0.7% above the third-quarter average at an annual rate. Implicit in our forecast of 2.6% GDP growth in the fourth quarter are increases in GDP over the three months of the fourth quarter that average 0.3% per month (not annualized).

Macroeconomic Advisers by IHS Markit's index of Monthly 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.

Posted 28 October 2018 by Ben Herzon, US Economist, Insights and Analysis, S&P Global Market Intelligence and

Kathleen Navin, Economics Executive Director, US Macroeconomics, S&P Global Market Intelligence