I am trying to find out whether the regime type of states signing international cooperation agreements influence the design of the agreement, more specifically whether the regime type of the members leads to the use of escape clauses. I will solely focus on bilateral agreements, so there are always and only two states that sign an agreement. Theoretically, I want to run a regression where my Y is binary 1 = there is an escape clause, 0 = there is no escape clause. My X is the regime type of the signing states, which is a continuous variable ranging from -10 to +10 (polity score). As there are always two countries signing the agreement, theoretically there are always two regime types that need to be included in the operationalization of X. My question is: should I use the distance (regime type 1 - regime type 2) between the regime types to operationalize my X, or should I use the average regime type score coming from both signing states? And how should I operationalize my control variables such as GDP per Capita, or age of the regime type? Should I also always use either the distance or the average between the two states?