arrests: # of murder arrests
countyid: county identifier: 1000*statefips + countyfips
density: population density; per square mile
popul: county population
perc1019: percent pop. age 10-19
perc2029: percent pop. age 20-29
percblack: percent population black
percmale: percent population male
rpcincmaint: real per capita income maintenance
rpcpersinc: real per capita personal income
rpcunemins: real per capita unem insurance payments
year: 1980-1996
murders: # of murders
murdrate: murders per 10,000 people
arrestrate: murder arrests per 10,000
statefips: state FIPS code
countyfips: county FIPS code
execs: # of executions
lpopul: log(popul)
execrate: executions per 10,000