A core feature of Legislative Outlook is a forecast of the likelihood that a bill will pass a particular stage of the legislative process. Users of State Net can weigh these forecasts alongside their own knowledge to make informed, data-supported decisions. Here we describe how Legislative Outlook forecasts work and provide guidance about drawing inferences from the information presented.
Legislative Outlook bill forecasts are created from State Net’s comprehensive federal and state legislative data.
Looking at state-by-state historical bill passage information we use machine learning to identify factors correlated with a bill’s passage at each stage of the legislative process. We customize our models for the US Congress and each state (plus the District of Columbia). Our models are also specific to each of 102 state legislative chambers. This work is done by our team of experts and Professor Mark Crain, a leading authority on quantitative analysis of government activity.
We’ve identified more than 40 factors that have significant forecasting power. These factors include, for example, the partisan composition of the chamber, the relevant legislative committees and past passage rates, the author’s leadership position and committee assignments, the author’s past success rate, and the bill’s current stage in the process.
Our models use these factors to forecast the likelihood of a bill passing a particular stage of the legislative process. This forecast is either Low (less than 40% chance), Medium (between 40-60% chance) or High (more than 60% chance). Accompanying each forecast, for comparison purposes, is the historic passage rate for all bills at the same stage in the prior session.
We regularly measure accuracy by comparing our forecast to end-of-session bill status. In 2018, Legislative Outlook forecasts were accurate more than 80% of the time (in other words, fewer than 1 in 5 forecasts were not correct). When a forecast is not correct, one cause can be information that Legislative Outlook can’t know, such as the bill’s author was not motivated to advance the bill.
Legislative Outlook is one ingredient for inference.
Effective legislative strategies require a combination of human judgment and data analytics. For a State Net user weighing a particular bill’s chance of passing to the next stage, she can now consider her own assessment of the bill’s merits and political support in the context of Legislative Outlook’s forecast. Legislative Outlook’s forecast may strengthen her own assessment or challenge her prior expectation, perhaps revealing new insights.
Overall, we believe the forecast from Legislative Outlook is a valuable tool for understanding the likelihood of bill passage. When combined with a user’s prior knowledge and judgment, Legislative Outlook can support informed, data-supported decisions.