computing untreated outcome for the treated

[jdramirezc]

What is the best to compute the untreated outcome for the treated? I am interested in compute the ratio of the treatment effect to the untreated outcome for the treated, which is similar to a percentage effect due to treatment, assuming the denominator is non-zero and that the outcome can only take positive values.

Is there a way to compute that parameter using the package? I'd appreciate any insights!