Minor coding errors were discovered in the data set after it was first given out.  
The files available for downloading on 
this site have the corrected results using 
the statistical county level tests employed in Ayres and Donohue's paper ("Shooting 
Down the More Guns, Less Crime Hypothesis").  The corrections involved a few 
thousandths of one percent of the data entries and occurred for observations after 
1996.  There were well  over 70,000 observations and over a hundred variables 
available in the  data set, we are dealing with a few hundred data entries that 
contained  mistakes. 

A couple of other specific comments might be in order regarding Plassmann and Whitley's conclusions.
1) The figures for the paper continue to show clear drops in violent crime for murder, rape, and robbery. I have redone these figures and they are available for being downloaded.
2) The figures for the paper continue to show clear drops in violent crime for murder, rape, and robbery. I have redone these figures and they are available for being downloaded.
3) Florenz Plassmann and Nic Tideman's paper in the October 2001 Journal of Law and Economics makes the strong case that the data should be treated as count data and Table 7 continues to show that violent crime rates decline after the law. In his Stanford Law Review paper, Plassmannagain makes the case that paper. As far as I can tell, Ayres and Donohue neither address the count data discussion nor in any way contradict those findings.. To see a general discussion of this and related issues please go to my blog site and see the discussion for 8/20/03.