Numerous controls were implemented to reduce bias and ensure the highest accuracy of the ratings. Firstly, all lawmakers were graded on the principles of limited government (expanding or shrinking government’s size, role or scope) as opposed to an ever-changing political philosophy. Secondly, certain social issues in which the limited government correlation varies (such as abortion) were excluded absent any government fiscal or operational implication. Finally, duplicative votes on the identical issue or votes on non-policy related actions (such as naming a post office) were excluded from the analysis.

Outside of the noted exclusions, every single vote taken in the previous year of Congress (January 1 through December 31) is included in the study and backed up by a full policy analysis and a limited government correlation statement.  A weighting system was implemented to account for the impact of the policy but limited to a three-point scale to reduce bias in implementation. In cases where lawmakers opposed a bill for entirely different reasons – such as conservatives opposing a bill for not enough spending cuts and progressive also opposing the same bill for too great of spending cuts – the roll call vote was dissected and scored by political party to ensure proper recording of viewpoint.

The ILA has developed the first-ever rating system that overlaps a lawmaker’s political ideology with the district they represent. The ILA’s “District Based Grade” is presented on an “A” to “F” scale with a grade of “A” presented to lawmakers whose Limited Government Rating meets or exceeds the level estimated for their district, and lower letter grades provided to lawmakers who fail to either exceed (i.e. Democratic lawmakers) their district estimates or fall short (i.e. Republican lawmakers).

The Cook Partisan Voting Index (Cook PVI) measures the partisan leanings of each congressional district. An estimated Limited Government Rating (LGR) is assigned to each congressional district based on the following formulas:

The District Alignment (DA) measures by how much a lawmaker exceeds (a positive number) or falls short (a negative number) their District Estimate. Democrat lawmakers receive higher letter grades the greater they exceed their District Estimate, and Republican lawmakers receive lower letter grades the greater they fall short of their District Estimate.