WISQARS is your friend
Go to the Centers for Disease Control's
WISQARS page; select
1. Homicide,
2. all injury,
3. Either select a state (pick from packing.org's list) or leave at United States, set the first year to 1981, the oldest data available,
4. go to the bottom of the page to 'select output groups' and if just one state, set to group by year, otherwise set to state, then year.
5. Submit request. Save the data
Then repeat, except at 2. select firearm; submit and save.
Draw lines across the data at the years you get for the effective date of CCW for that state.
Note that
generally the rates of murders continue to decline overall, and the rates of firearms murders continue to decline, and there is no obvious change in the 'rate of change' of that decline. Note there are ZERO occurrences of rates quadrupling, tripling, doubling, or increasing by as much as 50%.
There are lots of quibbles about exactly when a CCW law can be said to have 'taken effect'; I think a good working definition is 'the first full calendar year after the effective date of the law', that is, measurements for an entire measuring period, usually a calendar year, are needed to see what effect, if any, the law may have had on crimes. E.g. if Texas's law had an effective date of Jul 1, 2005, 'pre-CCW' would be through Dec 31, 2005, and 'post-CCW' would be from Jan 1, 2006 onwards.
The research to date is mostly John Lott's
More Guns, Less Crime ; that work has a lot of critics. The safest conclusion from the data is that CCW laws do NOT make things worse. Other claims for influence are
contentious , to say the least.