Why would one suppress the intercept in linear regression?

In a number of statistical packages including SAS, SPSS and maybe more, there is an option to “suppress the intercept”. Why would you want to do that?

Answer

If for some reason you know the intercept (particularly if it is zero), you can avoid wasting the variance in your data for estimating something you already know, and have more confidence in the values you do have to estimate.

A somewhat oversimplified example is if you already know (from domain knowledge) that one variable is (on average) a multiple of another, and you are trying to find that multiple.

Attribution
Source : Link , Question Author : user333 , Answer Author : Nick Sabbe

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