The correct answer to this open question is the following.
Although there are no options attached, or there is no specific reference to what kind of debates, we can comment on the following.
We assume you are talking about Presidential debates. If that is the case, then debates become more consistent since 1987 because, in this year, the Commission on Presidential Debates was created due to the initiative of the Democratic and Republican parties, in order to have a more professionally organized structure for the debates, so people could be more interested in the format.