Convergence Calculator
Pick a country, pick a growth rate it holds for the rest of the century, and the calculator says which World Bank income thresholds it crosses and in which year. The second mode builds the growth rate up from the three terms of the identity instead of asking you to guess it: output per worker, the employment-to-working-age ratio, and the working-age population.
Two things the arithmetic cannot hide. The income thresholds are GNI per capita on the Atlas method; the country cards carry GDP per capita in current dollars. They are different measures converted by different rules, so a crossing year is illustrative, not a forecast that the World Bank would reclassify anyone. And the second and third identity terms are prefilled from the cards where the cards carry them, on fifty-three of the fifty-four; on the card that does not, and on any field a source has not supplied, the box stays blank rather than filling itself with a plausible zero.
Set Nigeria to 4 per cent a year, the rate its GDP per capita grew at through the 2000s boom, and read off the year it reaches the lower-middle-income line. Now set it to 2 per cent, roughly the post-2014 record, and read the same line again. The gap between those two years is the whole argument of Part I, priced in decades rather than in percentage points.
Then switch to the second mode. All three boxes come prefilled from Nigeria’s card: a working-age population growing at 2.9 per cent a year, which is measured rather than modelled, and beside it the ILO’s modelled employment ratio and output per worker, the second of which is negative. Now type a zero into the lower two boxes: you have an economy in which output per worker never rises and no larger share of the working-age population finds work, and GDP still grows at 2.9 per cent a year while GDP per capita barely moves. That is growth without development, drawn in a single sum.
- At what sustained rate of GDP per capita growth does Nigeria reach upper-middle-income status before 2050? Compare that rate with what Korea, China and Vietnam actually managed over their own first twenty years, and say whether you would write it into a plan.
- Move the starting-year slider back five years and forward five. How many years does the lower-middle-income crossing move? What does that tell you about how much of the answer comes from the model and how much from a base year the card does not even record?
The calculator reads the same fifty-four records as the country cards, so a starting level here and a level on a card cannot disagree. The comparison overlay, Korea from 1965, China from 1980, India from 1991 and Vietnam from 1990, is drawn from Penn World Table 10.01 (Feenstra, Inklaar and Timmer, 2015): real GDP per head at constant national prices, set to 100 at each takeoff year, so each line is the shape of a growth path, not a dollar level. PWT’s China line grows more slowly through the 1980s and 1990s than China’s official national accounts do. What each field is and where it comes from is set out on the About the data page.