st: Stata drops the wrong level from regression using factor variables

[Nichole Szembrot <nes66@cornell.edu>]

I am having trouble getting Stata to omit the base level when I
include a factor variable with 2 levels in a regression. Instead of
dropping the base level, which I set using fvset, it includes the base
level then has to drop the level that I want to include due to
collinearity.

Here is the part of the code that creates the factor variable causing
the problem:

gen byte risk_averse = 1;
replace risk_averse = 2 if risk_preference == 5 | risk_preference == 6;
fvset base 1 risk_averse;

This is the code that I use:

reg voteVague_binary ibn.Treatment#ibn.RoundTypebyte
i.risk_averse#ibn.Treatment copy_indicator if contaminated==0
    & practice==0, noconstant vce(cluster id);

The first set of interactions, with all levels of Treatment interacted
with all levels of RoundTypebyte, works as it is supposed to. However,
instead of including a dummy for risk_averse=2 interacted with each
level of the Treatment variable, it includes a dummy for risk_averse=1
(the base level) and does not include the interactions that I actually
want.

I have even tried this, in an effort to force it to include the dummy
for level 2:

reg voteVague_binary  ibn.Treatment#ibn.RoundTypebyte
2.risk_averse#1.Treatment 2.risk_averse#2.Treatment
2.risk_averse#3.Treatment copy_indicator if contaminated==0 &
practice==0, noconstant vce(cluster id);

This generates the same result as the first one. Any ideas?
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