input famid inc1-inc12
1 3281 3413 3114 2500 2700 3500 3114 3319 3514 1282 2434 2818
2 4042 3084 3108 3150 3800 3100 1531 2914 3819 4124 4274 4471
3 6015 6123 6113 6100 6100 6200 6186 6132 3123 4231 6039 6215
end


foreach var of varlist inc1-inc12 {
  generate tax`var' = `var' * .10
}

list

foreach qtr of numlist 1/4 {
  local m3 = `qtr'*3
  local m2 = (`qtr'*3)-1
  local m1 = (`qtr'*3)-2
  generate incqtr`qtr' = inc`m1' + inc`m2' + inc`m3'
}

list incqtr1 - incqtr4