1999: About $400, from Agent readers
2000: About $1000, from Agent readers
2001: About $1100, from Agent readers and a short story sale at Strange Horizons
2002: About $1000, from Agent readers
2003: About $6000, from Agent readers and from first part of advance for Old Man’s War
2004: About $5000, from Agent readers and from first part of advance for The Android’s Dream
2005: About $15,000, from second part of OMW advance, first part of The Ghost Brigades advance, advance for Agent to the Stars hardcover, and short story sale to Subterranean Press.
2006: About $67,000.
I had already begun to figure out something like this was true because a friend who introduced me to John C. Wright as fantasy writer (I already knew him for space opera), was excited to discover they both work for the same software company.
So remember to keep your day job!