Hi guys,

I am trying to find which coefficient beta 1 or 2 has a greater effect on child mortality. i have carried out the reparameterisation trick ( or lincom command in stata), but stata omitted the water variable due to collinearity. my null hypothesis is Ho : beta 1 = beta 2 and alternative is H1: beta 1 > beta 2. the following is my regression model:

INFMORTUND~5= β_0+β_(1 ) SANITATION+β_2 WATER+β_3 logGDPPC+U

INFMORTUND~5= 146.1188 - 0.506 SANITATION - 0.015 WATER- 8.453 logGDPPC

my question is : when stata omitted water due to is it because of perfect collinearity?

Thank you