The Federal Reserve Bank of Chicago‘s national activity index, which measures the country’s overall economic activity, slipped into negative territory in February as the central bank noted continued weakness in the housing market. The Fed said a decline in consumption and housing activity offset positive economic data, causing the index to slip to -0.04 last month, compared to a positive index level of 0.01 in January. The Chicago Fed National Activity Index weighes 85 different economic indicators — including production and income, employment, unemployment, hours, personal consumption, housing, sales, inventories and orders — to compile its report. Even though housing continues to drag on the index, the Federal Reserve Bank of Chicago previously predicted improvement in the housing sector in 2011. In a report released a few months back, the Fed said it expects an increase in residential investments this year and at least a slight drop in unemployment. Write to Kerri Panchuk.