From my January 29 Xanga blog:
I'm in the process of updating my records and getting ready to visit our accountant. One thing I do at the end of each year--mostly because I can do it with the push of a button or two--is create a pie chart that breaks down my revenue streams.
I'm a full-time writer/editor and here's what generates income:
51.02% Editing non-fiction (primarily two publications)
26.10% Fiction (short stories and other less-than-novel-length fiction)
18.24% Advertising & Public Relations (writing press releases, print ads, TV commercials, brochures, etc.)
02.23% Non-fiction (primarily articles and essays)
01.07% Consulting (providing advice to other writers, editors, and publishers)
00.89% Royalties (primarily from novels and short story collections)
Most years 1-3% of my income is generated by paid speaking engagements, but I had no paid speaking engagements in 2005.
While it may be possible to earn a living writing fiction, I suspect most full-time writers--even if they call themselves full-time fiction writers--earn at least some part of their income from writing other things.