The idea that house prices double every 10 years has been repeated so often it's treated as a rule. But historical data shows it's true only about 55 percent of the time — and the 2020s are on track to be the weakest decade in 70 years.
The idea that house prices double every 10 years has become one of the most repeated axioms in New Zealand property culture. But Infometrics chief forecaster Gareth Kiernan has crunched the numbers, and the reality is more complicated — and more sobering for anyone counting on the rule to build wealth.
Looking at overlapping 10-year periods since 1950, Kiernan found that of 260 such periods, 143 — or about 55 percent — showed a doubling or more in nominal house prices. That means the rule has been true roughly half the time, and false the other half. "If there's one thing I hate, it's real estate agents trotting out the trope about house prices doubling every 10 years, which by these numbers is true more often than not, but without offering any explanation or rationale for it," he told RNZ.
How each decade actually performed
The data tells a starkly different story depending on where you started:
| Decade | House price growth | |--------|-------------------| | 1950s | 147% | | 1960s | 53% | | 1970s | 230% | | 1980s | 259% | | 1990s | 45% | | 2000s | 107% | | 2010s | 113% | | 2020s (so far) | ~10% |
The 2020s are currently on track to be the weakest decade for house price growth in the past 70 years. While the 1960s (53%) and 1990s (45%) also recorded slow growth, neither had prices rising by only 10 percent over a similar point in the decade. That weakness is consistent with REINZ data showing another flat month for the housing market in June 2026, as RNZ reported.
Cotality chief property economist Kelvin Davidson said the rule held partly because of specific conditions: falling interest rates, the rise of two-income households, constrained land supply, and a relatively favourable tax treatment of property. "Does it hold from here on? I've got my doubts," he said. "If you think about some of those things that have driven house prices up, they just can't apply any more."
Interest rates have already fallen to historically low levels, politicians on both sides are signalling intent to increase land supply, and the tax system could become more restrictive for property investors. Davidson said a growth rate of 4 to 5 percent might be more normal going forward. "If you go to a 4 percent growth rate it's going to take 18 years to double. It does sort of push out that horizon to quite a bit longer period of time."
A turning point in expectations?
Davidson noted a shift in investor sentiment. "People are starting to question the assumption and possibly thinking about property investment differently." He acknowledged the risk of declaring "this time is different" but said the structural drivers that previously supported rapid price growth had materially changed. Property investor Steve Goodey took a more cyclical view, arguing that the market had been here before — where pessimism was at its peak — and that recovery typically followed. But even he estimated an average of seven years rather than 10 for properties to double in value, and noted that the next upswing was unlikely to arrive within the next year or two.
The broader implication for personal finance is that assumptions built on the "every 10 years" rule — whether for retirement planning, investment property decisions, or equity release strategies — may need to be recalibrated.
This article is for general information only and is not personalised financial advice. Seek advice from a licensed financial adviser (registered on the FSPR) for guidance specific to your situation.