Visualizing the legislative process with Sankey diagrams

Kamil Gregor at “The process of shaping the law often resembles an Indiana Jones maze. Bills and amendments run through an elaborate system of committees, sessions and hearings filled with booby traps before finally reaching the golden idol of a final approval.
Parliamentary monitoring organizations and researchers are often interested in how various pieces of legislation survive in this environment and what are the strategies to either kill or aid them. This specifically means answering two questions: What is the probability of a bill being approved and what factors determine this probability?
The legislative process is usually hierarchical: Successful completion of a step in the process is conditioned by completion of all previous steps. Therefore, we may also want to know the probabilities of completion in each consecutive step and their determinants.
A simple way how to give a satisfying answer to these questions without wandering into the land of nonlinear logistic regressions is the Sankey diagram. It is a famous flow chart in which a process is visualized using arrows. Relative quantities of outcomes in the process are represented by arrows’ widths.
A famous example is a Sankey diagram of Napoleon’s invasion of Russia. We can clearly see how the Grand Army was gradually shrinking as French soldiers were dying or defecting. Another well-known example is the Google Analytics flow chart. It shows how many visitors enter a webpage and then either leave or continue to a different page on the same website. As the number of consecutive steps increases, the number of visitors remaining on the website decreases.
The legislative process can be visualized in the same way. Progress of bills is represented by a stream between various steps in the process and width of the stream corresponds to quantities of bills. A bill can either complete all the steps of the process, or it can “drop out” of it at some point if it gets rejected.
Let’s take a look…”