Back end "calculation" tests

[emma-nechamkin]

The following tests can be unit tests to check the accuracy of each calculation:

• [x] Ag value percentile is calculated correctly (floored properly)
• [x] Ling iso is not included for PR in the percentile
• [ ] Imputation of income

We also have some analysis-type tests we should run as more of "smell tests"

• [x] Distributions of each raw variable
• [x] Counts of tracts exceeding 90th percentile