// reestimate using IV
qui ivregress 2sls so2 (pop = temp precip) manuf wind

qui probit hiso2 pop manuf hiprecip

keep state region pop popurb medage marr divr 

                           // check pop
list if  !inrange(pop, 300000, 3e7)  

keep state region pop popurb medage marr divr 

list state region pop in 1/5

list state region pop in 1/5

summarize medage if pop > 5000

describe pop smallpop largepop popsize urbanized

list region state pop totpop, sepby(region)

list region popsize state pop meanpop2, sepby(region popsize)

mean pop popurb

list state pop in 1/5

tabstat pop, stat(mean min max) by(size)

list state medage pop if inrange(pop, 5000, 9999), sep(0)

label var pop "1980 Population, '000"

generate urbanized = popurb / pop

replace smallpop = 1 if pop <= 5000 & !missing(pop)

generate smallpop = (pop <= 5000)

generate smallpop = (pop <= 5000) if !missing(pop)

label variable smallpop "States with <= 5 million pop, 1980"

by region: generate totpop = sum(pop)

bysort region popsize: egen meanpop2 = mean(pop)

// undocumented egen avgpop = mean(pop), by(size)
bysort size: egen avgpop = mean(pop)

quietly regress so2 temp manuf pop

quietly regress so2 temp manuf pop wind precip days

eststo: quietly regress so2 temp pop wind

// estimate with OLS
qui regress so2 pop manuf wind 

qui probit hiso2 pop manuf

list pop mo1 so2 mv1, sep(0)