Chore 🧹: review and update household income categories

[mnbina]

Background
Income category breakpoints were used as is, directly from MTC. The Year $$ in the MTC Example model and the income in the Bay Area is different from the CTPS region. These should be updated to reflect the CTPS region context.

Goals
The appropriate shares of households should be allocated to the different income bins, specific to the CTPS region.

[mnbina]

MTC Example prototype assumes year 2000 cents.
In places, there are the following categories: 0-30, 30-75, 75+; Low = 0-20, Med = 20-50, High = 50-100, Very High = 100+.
Assuming these are tertile and quartiles, the following can be assuming for CTPS:
Tertiles: 0-50, 50-90, 90+
Quartiles: 0-35, 35-70, 70-140, 140+

These assumptions are based on ACS 1-year data for Massachusetts (shown below in 2024 $), where the following was assumed:
Tertiles = 0-65, 65-125, 125+ (note that the breakpoint are too aggregate for this level of breakdown - these should be reviewed and revised later, ideally in estimation)
Quartiles = 0-50, 50-100, 100-200, 200+

These 2024$ breakpoints were scaled down to 2010$ breakpoints, using CPI data from BLS, which shows a scaling factor of 0.70 to go from 2024$ to 2010$.

[mnbina]

Note that this should be revisited after all new components from SANDAG components are added. For example, telecommute frequency has another set of income categories from the SANDAG specification.