The ADP National Employment Report^® is a measure of nonfarm private employment, based on a subset of aggregated and anonymous payroll data that represents approximately 400,000 of ADP’s 500,000 U.S. business clients. The release for March begins as follows:

Wednesday, April 1, 2009, 8:15 A.M. ET
Nonfarm private employment decreased 742,000 from February to March 2009 on a seasonally adjusted basis, according to the ADP National Employment Report®. The estimated change of employment from January to February was revised down by 9,000, from a decline of 697,000 to a decline of 706,000.

FT reports the ADP number for this month is foreboding for the Friday non-farm payrolls number:

“The ADP survey sent ripples of concern through markets on Wednesday that the US government’s monthly jobs data – seen as one of the most important indicators of the US economy’s health – would also be dire when released on Friday.

“It’s a terrible number. It is almost a loss of three quarters of a million jobs which is possibly the highest we have seen so far over the length of this crisis. Obviously [it is] foreboding ahead of [Friday’s] non-farm payrolls report,” said Matt Esteve, foreign exchange trader at Tempus Consulting.”