Dear all,

I'm helping my prof modify past code to adjust to the new dataset. It is my first time using globle parameter to navigate through files. I have a separate dofile for all global parameters, and inside there is this global parameter:
Code:
global weight_var                                 weight_worker
And in my statistic calculating do file, when use this parameter, it write
Code:
keep $wage_definition_ts ${weight_var} $gender_groups
, while you can see all other global parameters are not in { }.
I want to ask what is the difference if I put it in {} and not?

Thanks!