I'm researching for a book on the IT industry.  How many
microprocessors are there in the average home, and (less important) at
what rate is it rising?  Please quote sources in your answer.

computer, calculator, microwave, auto, Tv. frig, heating system, top cars

My guess is 12.  Wonder what the answer will be?

modern washing machines and dryers

"There are approximately 50 microprocessors in an average middle-class
American household today"

Source: College of Engineering Signatures, Notre Dame
http://www.nd.edu/~engineer/publications/signatures/2003/wayoflife.html

The answer - according to the Notre Dame article - is about 200, once
you've tossed in a car and a couple of games consoles.  With a MTBF of
about 200,000 hours, you can expect about four failures a year, which
seems to bear out my experience.

Thanks to all those of you who commented

Martin Farncombe