Obtain or generate historical geometries for FERC 714 Planning Areas

[zaneselvans]

The 2018 geometries for FERC 714 Planning Areas are available from HIFLD, but the geometries and associated respondents from previous years are different, so we need something more to do historical analysis...

• [x] Reach out to FERC folks and see if they have the historical geometries (Nope!)
• [x] Ask LBL if they have historical geometries.
• [x] Reach out to EIA folks and see if they have the historical geometries.
• [x] See how much the list of planning area respondents changes from year to year in FERC 714 data.
• [ ] Compare the 2018 Planning Areas to the utility service territories -- can we infer areas from respondent IDs?

[zaneselvans]

Just FYI: about 88% of all the reported demand from FERC 714 is associated with one of the geometries in the 2018 HIFLD data. Going back in time, this eventually drops to about 58%. So there's a lot of additional information to be gained by cobbling together complete geometries, especially in prior years.