The Chicago National Activity index sinks ever deeper and is now at its weakest since the 1973-75 recession, when the index troughed at -3.94. In January, the 3- month average CFNAI index, the preferred gauge, fell to a new low of 3.41 from a revised -2.70 in December. The monthly index showed a modest improvement to - 3.45 from a downwardly revised 3.65 in December, earlier reported as -3.20. In the Chicago Fed methodology, a value below -0.70 means that the economy has fallen into recession with a 70% probability. The report confirms the early indications from the manufacturing survey that the pace of the downturn has not yet stabilized.