Consistent variable names in output dictionaries

[jdebacker]

Names for the same variables differ between the SS output dictionary and the TPI output dictionaries, e.g., Y and Yss. This can make a little more difficult to pull from both (maybe not too hard to recall to append the ss, but can't easily loop over a list of variable names and pull from both the SS and TPI output with same list).

Thoughts on making names consistent?