The Business Conditions Index, a leading economic indicator derived from a monthly survey of supply managers in the Midwest, sank to 50 in December from 52.6 in November.

The index, which ranges between 0 and 100, is a mathematical average of indexes for new orders, production or sales, employment, inventories and delivery lead time. In Iowa, the index slipped from 57.7 in November to 56.3.

The Creighton Economic Forecasting Group has conducted the monthly survey of supply managers in nine states since 1994. States included in the survey are Arkansas, Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, Oklahoma and South Dakota.