American Factories Have br Worst Month Since 1946 U.S. industrial production br plunged 5.4 in March, the br largest drop since January 1946. The last time U.S. factories experienced a similar br decrease was during the shift from wartime to br consumer products at the end of World War II. The drop comes as many factories making autos, br aircraft and other goods halt production to br protect workers from the spread of COVID-19. Citi economists, br via CNN The data shows the impact of weaker demand and br social distancing in the workplace, according to ING br chief international economist James Knightley.