Replace other_medical_expenses with a CMS NHEA out-of-pocket benchmark

[MaxGhenis]

other_medical_expenses is currently calibrated using a survey/account-style benchmark. If we keep a national non-premium medical spending target, CMS National Health Expenditure Accounts (NHEA) out-of-pocket spending is the more defensible official aggregate.

Why the current target is weak:

• The current benchmark is not a clean administrative series.
• NHEA out-of-pocket spending is the official macro aggregate for household medical out-of-pocket spending.
• It is still account-based rather than purely administrative, but it is more authoritative than a survey-preservation target.

Proposed change:

• Replace other_medical_expenses with an explicit NHEA out-of-pocket benchmark, documenting any adjustments needed to exclude premiums and align to the model concept.
• If the concept mapping is too loose, demote the target to diagnostic status rather than treating it as a hard anchor.

Primary sources:

• CMS National Health Expenditure Data: https://www.cms.gov/data-research/statistics-trends-and-reports/national-health-expenditure-data
• CMS NHEA definitions, sources, and methods: https://www.cms.gov/files/document/definitions-sources-methods.pdf