The chart above shows total sales per quarter across the entire US for each quarter from 1992 through Q1, 2007. This data is taken from the US Census Bureau's Quarterly Financial Report.
The chart clearly shows not only the drop off in manufacturing sales during 2001 and 2002, but also the dramatic reduction in income after tax during this period. From 2004 onwards there has been a return to profitability across the manufacturing sector, and more recently a steady trend to profitability levels even higher than the late 1990s.
Given the reduction in total manufacturing employment covered in a previous post, one can assume that keeping payroll costs in check while output is rising is having a major contributor to the increased margins that US manufacturing companies are achieving.