Using data from
http://149.101.22.40/dataonline/Search/Crime/State/statebystaterun.cfm?s
tateid=9
(you may need to cut-and-paste both lines of the above URL to get it to
work), I calculated the following, the entries of which show the average
homicide rate over the surrounding five years (e.g., the entry for 1971
shows the average homicide rate for the period 1969-1973).
I started with 1968 to see what happens on both sides of the year 1971,
which Tim was interested in (that year's rate having possibly been
cherry-picked by Lott due to being unusually high).
I went all the way out to 1988 to see what happens on both sides of the
year 1985, which Tim was interested in (that year's rate being lower
than in 1976).
1968 -- 25.76
1969 -- 29.68
1970 -- 31.84
1971 -- 34.20
1972 -- 34.66
1973 -- 35.38
1974 -- 33.32
1975 -- 32.32
1976 -- 30.74
1977 -- 28.56
1978 -- 28.30
1979 -- 29.96
1980 -- 30.54
1981 -- 30.82
1982 -- 30.96
1983 -- 29.36
1984 -- 28.54
1985 -- 29.64
1986 -- 35.66!
1987 -- 44.22!!
1988 -- 55.28!!!
I'm no statistician, so this method of evening out the bumps may be
wrong-headed, but assuming they're not hopelessly wrong, these data show
that Tim's charge of cherry-picking is baseless. Lott's assertion that
the rate started to trend down well before the law appears to be
correct.
The rates were trending:
UP from 1968 to 1973
DOWN from 1974 to 1978
UP from 1979 to 1982
DOWN from 1983 to 1984
UP (skyrocketing, really) from 1985 to 1988
Tim claimed
"Also by presenting rates for just 1971 and 1976, they make it look
as if the rates were decreasing before the law, instead of going up and
down."
The truth is that the rates really were clearly trending down
starting a couple of years before the law.
Tim claimed
"If you choose one year at random to represent the situation after
the law was passed their is a good chance that it will be
unrepresentative. Of course, they didn't just choose one year at random.
They chose 1981, which just happens to be the year that had the highest
homicide and robbery rates of the ten following years."
The truth is that the above data show two things:
1) 1981 was not really anything special as far as the trends go
(it's near the end of a period of relatively gradual upward trends,
having just barely made it back up to the 1976 figure), and
2) if you keep checking on out to 1988, the trend really skyrockets,
causing one to wonder if that treacherous Lott is simply not very
skilled at cherry-picking.
BTW, IMHO, this data doesn't suggest that there was anything special
about 1976, either -- it's just smack in the center of a 5 year downward
trend.
Peter
