Tri-County Affordability, 2000–2025
What share of a median income it takes to buy a median home
Affordability usually gets discussed in feelings. The market's crazy. Nobody can buy here anymore. This is the arithmetic underneath the feeling: one number, per county, per year. Drag the slider and watch where the line crosses.
The tinted band is everything above 100, where the median home costs more than the median household earns.
Reading the index
The number is a percentage of income, so it reads straight across. Three reference points:
The three moving parts
The index is not one thing. It is three, stacked on a shared timeline so you can trace cause down to effect. The gap between price and income is structural and it only widens. The mortgage rate is cyclical and it swings hard in both directions. The index at the bottom is what the two produce together. Drag the year slider above, or hover the panels, to move the marker through all three at once.
What waiting costs
Here is the part the index above cannot show you. The index is the cost of entry, and it resets every year for every new buyer. But a buyer who already owns is not paying the index anymore. Their principal and interest was fixed on closing day and it never moves again, while income around it keeps climbing. Pick a purchase year and watch the two diverge.
Both lines are in index units: the share of that year's median household income it takes to carry the payment.
The full series
Median sales price, median household income, the prevailing 30-year fixed rate, and the resulting index. Values above 100 are shown in red. Click any row to move the charts to that year.
How this is built
The index. Assume 20% down, a 30-year fixed at that year's average rate, and that a lender qualifies a buyer at 25% of gross income toward principal and interest. Qualifying income is the income needed to carry that payment. The index is qualifying income divided by median household income, times 100. This is the standard Realtor-association affordability index inverted, so the number reads directly as a percentage of income rather than as a score where higher is better.
The locked-payment line. A buyer who closes in year Y carries the same principal and interest for the life of the loan. Expressed against a later year's median income, that fixed payment falls as incomes rise. The line is the purchase year's index, scaled by the ratio of purchase-year income to current-year income. Three things it assumes: that the household's income tracks the county median (yours may run ahead of it or behind it), that the buyer holds the loan rather than refinancing or moving, and that principal and interest is the whole payment. It is not. Taxes, insurance, HOA dues and PMI are excluded from every number on this page, and in this market insurance in particular has grown faster than anything else here.
Median sales price. County-level annual medians published by the Charleston Trident Association of REALTORS® MLS are used directly for 2013 through 2017 and 2021 through 2025. For 2000 through 2012 and 2018 through 2020, CTAR did not publish a county annual median in a form available here, so the series is extended backward using the FHFA All-Transactions House Price Index for each county, a repeat-sales index calibrated to that county's own transactions, anchored to the nearest published CTAR median. Those years are marked est. Treat them as directionally sound rather than exact. A repeat-sales index tracks the same homes reselling, while a median tracks whatever happened to sell, so the two can drift a few percent apart in a market with heavy new construction. Berkeley and Dorchester are the most exposed to that.
Median household income. U.S. Census Small Area Income and Poverty Estimates, by county, through 2024, the most recent published year. The 2025 figure is a placeholder at 3.5% growth and will need replacing when SAIPE publishes.
Mortgage rate. Freddie Mac Primary Mortgage Market Survey, annual average of the weekly 30-year fixed rate.
What this is not. Every figure here is a county median. A median is a summary of thousands of transactions and it describes no actual household. Nothing on this page is a forecast, an appraisal, or advice about when to buy or sell.
Sources. Charleston Trident Association of REALTORS® MLS annual reports (2017, 2025); U.S. Federal Housing Finance Agency; U.S. Census Bureau SAIPE; Freddie Mac. Retrieved via FRED, Federal Reserve Bank of St. Louis.
Where this leaves you
A median is a fact about a county, not about your household.
These lines tell you what the middle of the market faces. They cannot tell you what your income, your down payment, your rate lock, or the three neighborhoods you would actually live in add up to, and those four things move the answer more than any county line does. That part is a conversation, and it is a short one.
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