Parameter gamma
controls interactions between spillover effects.For gamma
=1 for ever $1 given to a member of a group, each member receives $1N_i_group
no matter how many others are already treated.
For gamma
>1 (<1) for ever $1 given to a member of a group, each member receives an amount that depends negatively (positively) on the number already treated.
The default estimand is the average difference across subjects between no one treated and only that subject treated.