WASHINGTON (AFX) - The US economy contracted at a 1.3 pct annual rate in the third quarter, slightly weaker than the previous estimate of a 1.1 pct decline, the Commerce Department said. This is the largest quarterly decline in GDP growth since the first quarter of 1991. The final revision to Q3 GDP growth was weaker than expected. The consensus forecast of Wall Street economists was for Q3 GDP to be unrevised at down 1.1 pct. This is the third and final revision to Q3 GDP. The first estimate of Q4 GDP will be released on Jan 30, 2002. Most economists expect a negative growth rate for the fourth quarter. The downward revision to Q3 GDP was due to weaker government spending and fewer exports than previously estimated. The report did not change the fundamental picture of the third quarter where weak business investment and a record decline in inventories offset a small gain in consumer spending. Inventories subtracted slightly more from Q3 GDP growth than previously thou ght. Businesses subtracted a record 61.9 bln usd from inventories in the third quarter, down from the previous estimate of 60.1 bln. The real change in business inventories subtracted 0.81 percentage points from Q3 GDP growth, slightly more than previous estimate that inventories subtracted 0.75 percentage points. Final sales -- GDP growth minus inventory behavior -- declined at a revised 0.5 pct in the third quarter, down from the previous estimate of 0.3 pct fall. Consumer spending in the third quarter was revised down to a 1.0 pct gain from the previous estimate of a 1.1 pct rise. This is the smallest increase in consumer spending since the first quarter of 1993. The trade sector subtracted more from Q3 GDP growth than previously thought. Trade subtracted 0.27 percentage points from Q3 GDP growth compared with the previous estimate of a 0.16 percentage point drop. Exports were revised to a fall of 18.8 pct, down from the previous estimate of a 17.7 pct fall. Imports were revised to a fall of 13.0 pct, down slightly from the previous estimate of a 12.9 pct fall. Government spending rose a revised 0.3 pct, down from the previous estimate of a 0.8 pct increase. Inflation was revised slighly higher in the third quarter. The GDP chain weighted price index rose 2.3 pct, up slightly from the previous estimate of a 2.2 pct rise. Excluding food and energy prices, the GDP chain-weighted index rose 2.8 pct, also up slightly from the previous estimate of a 2.7 pct rise. The consumption price index fell 0.2 pct in the third quarter, up from the previous estimate of a 0.3 pct fall. Excluding food and energy prices, the PCE price index was up 0.5 pct, also up slightly from the previous estimate of a 0.4 pct rise.