-0.5 + -6.3 + -6.1 = -12.46[%]
The -12.46% stands for the shrinkage of the US economy since 01-07-08, so 3rd. and 4th. quarter 08 as well as 1st. quarter 09; nine months.
This is still quite an artificial number, far from being punchy.
You will find more numbers here, e.g. +0.4, -23.0, -51.8 which end up at 37.3% of what it was on July 1st last year, a recess of round about 63% representing the decrease of the 'gross private domestic investment'.
This is like a ship that under full steam drops anchor; like a complete economy going on strike; I guess tax revenue will mirror that.