House Price Index Year-Over-Year Change, Explained
The year-over-year figure from a house price index is one of the most quoted numbers in housing, and also one of the most misunderstood. It compares a price level today with the same month a year ago. Here is what it captures, what it hides, and how it feeds the phase labels.
- Year-over-year compares the index to the same month a year earlier, which removes ordinary seasonal swings.
- A positive figure means higher prices than last year, but says nothing about the pace in recent weeks.
- It can lag turning points because it averages across twelve months of change.
- The figure is one of two core inputs to each county's phase label.
The idea in plain words
A house price index tracks how values move over time, usually by following repeat sales of the same properties or adjusting for differences in homes sold. The year-over-year reading takes the latest value and compares it to the same month last year. If the index went from one hundred to one hundred and three, the figure is three percent. The index itself has no meaning in dollars; only the change matters.
Why a full year is used
Housing sales cluster in spring and summer and thin out in winter. Comparing a June figure to a March figure would mix real movement with seasonal effects. Looking at the same month a year apart sidesteps that noise. The price paid is a steadier measure, even though waiting twelve months for a comparison means recent shifts take time to be felt in the number.
The lag problem
Because the figure spans a full year, it can keep showing positive growth for a while after prices have begun to cool, and it can stay negative after a rebound starts. Think of it as a rear-view mirror with a slightly long delay. That is one reason the phase system also uses drawdown from peak, which responds differently and helps catch what the annual rate alone misses.
Averages hide the local story
A state or metro index averages many neighborhoods. Within it, one town may be surging while another slides. When a county's number is borrowed from the metro area or state series, the county inherits that average. Always check which series is behind the figure before concluding anything about a particular community or street.
How the radar uses it
The phase rules treat the annual change as the speed gauge. Strong positive speed near a high points toward expansion or peak, negative speed points toward contraction, and near-zero speed with little drawdown points toward neutral. Combined with the second input, it lets a simple rule set produce labels that stay consistent from one county to the next.
The latest reading
Across 3,150 counties in the June 2026 run, the average year-over-year price change is 3.1 percent.
House Price Index Year-Over-Year Change, Explained: questions
Is year-over-year change the same as inflation?
No. It tracks home prices specifically, not general consumer prices. The two can move together or apart. Comparing them is common, but each is built from different data and answers a different question.
What does a negative year-over-year number mean?
It means the index is lower than the same month last year. It does not by itself reveal how deep the decline is from an earlier high; that requires the drawdown reading.
Why do different sources report different numbers?
Indexes vary in method, geography and data sources, such as repeat sales versus median sale prices. As a result, two reputable sources can report different annual changes for the same area and month.
Can year-over-year change miss a turning point?
Yes. Because it averages twelve months of change, it can lag a recent shift. That is why looking at momentum history and drawdown helps spot turns the annual figure has not yet registered.