Prices paid by consumers in the United States and its main non-communist allies in 1984 showed the smallest rise in 12 years, the International Monetary Fund reported. The average increase in 21 countries was 4.8%, which the fund called a sharp overall drop from the 5% of 1983. Although the United States had a below-average inflation rate of 4.3%, its 1984 rate was higher than the 3.2% of 1983. The average money supply, a major element in inflation, grew by only 7% in the 21 countries. It was 9.9% in 1983.