The list in this appendix shows how we have grouped different “last actions” into the categories we use for our Disposition variable. Under the header for each category, we list last actions that we have grouped into that category.

Unfortunately, the phrasing used to report this information on Thomas – and hence in our dataset – is not uniform, either across or within Congresses. For example, if the last action is the tabling of the amendment, this action might be described either as “Fell when tabled” or as “Motion to table amendment agreed to in Senate by yea–nay vote.” In the following list we have standardized such alternative descriptions of the same action.

In our coding we have made some subjective decisions, which we discuss briefly. First, we have separate Modified and Adopted categories, rather than a single Adopted category, in order to easily distinguish these categories from one another, although we think it probably makes little sense to distinguish them for many purposes. One situation in which distinguishing them might be useful is the study of roll call votes on amendment adoption. Because our data include only the last action on an amendment, and modification comes after adoption, it is possible for amendments in the Modified category that there was a roll call vote on adoption that is not included in our data.