correlation and causality examples

My favorite example on correlation !-> causation is data from Yule & Kendall
on the relationship between number of licenses for radios and the number
of people classified as 'mental defectives' in England and Wales from 
1924-37

Of course, both were increasing over time, the latter due to increase in 
diagnosis
using this term, the former due to increased availability, accounting 
for the very
high correlation.  I've attached the data as a SAS file.

Subject:
[R] correlation and causality examples
From:
Jean lobry <lobry at biomserv.univ-lyon1.fr>
Date:
Sat, 15 Nov 2003 15:49:29 +0100
To:
r-help at stat.math.ethz.ch


Dear All,

I'am looking for examples showing that correlation does not imply
causality, the targeted audience consists of undergraduate students
(their first year at the university but in the BioMathStat track).
All practicals are under R.

Michael Friendly     Email: friendly at yorku.ca 
Professor, Psychology Dept.
York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
4700 Keele Street    http://www.math.yorku.ca/SCS/friendly.html
Toronto, ONT  M3J 1P3 CANADA