Mountain to Climb

How economic convergence is calculated

Mountain to Climb is an economic convergence calculator. It answers one question: if a poorer economy (the chaser) and a richer one (the target) each grow at a stated annual rate, when does the chaser catch up?

The formula

If the chaser starts at value C and grows at rate g, and the target starts at T and grows at rate h, the gap closes when C(1+g)^t = T(1+h)^t. Solving for t:

t = ln(T / C) / ln((1 + g) / (1 + h))

The answer depends only on the starting ratio T/C and the growth differential. If g is not greater than h the chaser never catches up. If C is already at or above T, the chaser is ahead and t = 0.

Start year

Projections start the year after the latest year for which both countries have observed data (or a chosen base year, if later). Values are grown forward from the latest shared observation using the stated rates.

Scenarios, not forecasts

Results follow only from the growth rates you choose. Compare pages default each country to its own trailing 10-year compound annual growth rate, which describes the past, not the future.

Required growth by a deadline

To match the target by year Y, starting n years after the latest shared data, the chaser needs growth g = (T / C)^(1/n) x (1 + h) - 1.

Indicators and data

The default indicator is GDP per capita, PPP (constant 2021 international dollars, World Bank NY.GDP.PCAP.PP.KD). PPP adjusts for local price levels and suits comparing living standards; nominal US-dollar GDP per capita moves with exchange rates. Other indicators come from the World Bank, OECD, UN World Population Prospects, Our World in Data, Ember and IRENA.

Data caveats

Some countries' GDP per capita is distorted by structural factors: Ireland (multinational profit booking), Luxembourg (cross-border commuters), Qatar and the UAE (large non-citizen workforce), Singapore (financial hub). API and compare pages use the published figures by default and list these caveats; the interactive app can apply adjustment factors.

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