How to calculate birth year effects?

[Bright Tree]

Dear friends,

I hope to calculate the birthyear effects. My code is similar as below,

reg income i.birthyear i.cohort, noconst

But most dummies of i.cohort are missing. Thank you for any advice.

[William Lisowski]

Is your "cohort" variable based on age? If so, i.birthyear and i.cohort will be largely collinear, and (since i.cohort followed i.birthyear in your reg command) most of the cohort indicators are fully determined by the birthyear and thus are eliminated.

[Bright Tree]

Prof.Lisowski, thank you so much for your advice. But, can I control the cohort effects in another way?

[Rich Goldstein]

you might try one of the user-written age/period/cohort modules; there are at least 4; type

ssc describe a

and scroll to -apc- to see the 4 (the others are called -apcd-, apcgo and apch); note that your overall strategy and aims are entirely unclear to me so this is just a guess