Do Researchers and Slum share of urban population go together across countries?

Across 128 countries the link before adjusting for anything is r = -0.56, on a scale from -1 (opposite) to +1 (in step). A version that uses only each country's rank gives -0.80.

Does the link hold within countries over time, not just across countries?

Comparing each country only with itself across 2000-2022, and setting aside what happened worldwide in each year, the link is +0.346 (59 countries, 593 country-years). Using year-to-year changes, it is —.

Does Researchers cause Slum share of urban population?

This analysis cannot answer that. It shows only that the two go together. A link between two country measures, adjusted or not, does not show that either one changes the other. Country figures also say nothing about individual people.

Researchers vs. Slum share of urban population

Fades after adjusting for income

Across 128 countries, Researchers and Slum share of urban population rise and fall together at r = -0.56 (on a scale from −1 to +1, where 0 means no link). Comparing only countries with similar income (GDP per person) shrinks it to -0.01, which could easily be chance (q = 0.98, allowing for the many pairs tested, and allowing for countries in the same region being alike). So the first figure mostly shows richer countries differing from poorer ones, not a link between these two things. Caution: sign flips when a single country is removed.

Comparing countries across the middle half of researchers, 139 to 2,729 per million people, slum share of urban population is better by 14.1% of urban population at the top of that range than the bottom. Comparing only countries with similar national income, the gap is 0.112% of urban population.

Link before adjusting (r)-0.555p = 1.0e-11 · 128 countries

After adjusting for national income-0.005p = 0.951 · likely range [-0.18, +0.17]

p, allowing for regions0.955standard error 0.094 · 7 regions

Check for luck (q)0.976across 12,497 pairs

How to read these.r runs from −1 (one goes up as the other goes down) to +1 (they rise together), and 0 means no link. Adjusting for national income means comparing countries with the same GDP per person, so differences in wealth can’t explain the link. Income is used in percentage terms, since an extra $1,000 means more to a poor country than to a rich one. p is how likely a link this strong would be if there were really none. Below 0.05 means it is unlikely to be chance. Very small values are written in short form: 1.1e-32 means a decimal point followed by 31 zeros and then 11, so very close to zero. The likely range is where the true figure probably lies, and a range that crosses zero means the link could easily be chance. Countries in the same region tend to resemble each other, so the third figure allows for that, which gives a fairer p. The standard error is the typical size of the error in r. Finally, testing this many pairs means some will look strong by luck alone. A q below 0.05 means this link is unlikely to be one of those.

Researchers · per million peoplelink with income +0.85 · proxy

Slum share of urban population · % of urban populationlink with income -0.78 · high

Both of these rise and fall closely with national income, so a strong link between them before adjusting was close to certain. Read the adjusted figure, not the first one.

“Link with income” is how closely each measure tracks GDP per person across countries, from −1 to +1.

Every country as a dot

best-fit line line after adjusting

Four ways to measure the link

Method	r	p	Countries
Standard (Pearson), not adjusted	-0.555	1.0e-11	128
By rank (Spearman), not adjusted	-0.801	7.2e-30	128
Standard (Pearson), adjusted for national income	-0.005	0.951	128
By rank (Spearman), adjusted for national income	-0.262	0.003	128

The rank version uses only each country’s place in line, from lowest to highest, so a few extreme countries count for less. The adjusted and unadjusted versions use the same 128 countries: those that report both measures and GDP per person. So the gap between them comes from the adjustment, not from a change in which countries are counted. Drop in the size of r after adjusting: +0.550 (a minus sign means it grew).

How solid is it?

Leaving out one country at a time, r ranges from -0.023 (without SGP) to +0.024 (without BRN). The bar above shows that range on a scale from −1 to +1, with the solid line at the full result. The single country that moves r most: BRN (+0.030).

Fragile: this link may not hold up.

sign flips when a single country is removed

Within each region

Countries are not separate, unrelated cases, and neighbors share a lot. A link that holds inside each region is far more believable than one that shows up only when comparing regions.

	n	r
East Asia & Pacific	16	-0.20
Europe & Central Asia	45	-0.10
Latin America & Caribbean	16	-0.01
Middle East, North Africa, Afghanistan & Pakistan	17	-0.06
Sub-Saharan Africa	29	-0.12

By income third

If the link shows up only in the richest third of countries, it is a feature of rich countries, not a general pattern.

	n	r
Poorest third	43	-0.39
Middle third	42	-0.04
Richest third	43	-0.24

By largest religious group

Countries grouped by a label they share, such as main religion, rather than by a number. Groups of fewer than twelve countries are not shown. These groups differ in income, region and history all at once. So a gap between them is a place to start asking questions, not an answer.

	n	r
Christians	79	-0.03
Muslims	32	-0.10

By last european coloniser

	n	r
France	13	-0.44
Never a European colony	15	+0.30
Spain	16	-0.25
United Kingdom	36	-0.18

Without outliers (countries far outside the middle half of countries on either measure, by more than one and a half times the width of that middle half): r = -0.055 after dropping 7 countries.

Two series, one country

Both measures over the years for one country you pick. The two charts are stacked so they share only the years along the bottom.

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Over time, within countries

Everything above compares countries with each other at one moment. This section compares each country only with itself over 23years. So a link here can’t come from anything about a country that stays the same, such as its history, geography, institutions or culture.

The link shows up within countries over time (r = +0.346) but mostly disappears in year-to-year changes (r = —). That points to slow trends particular to each country, not the two measures moving together from year to year.

Across countries (adjusted)-0.005for comparison

Within countries-0.085each country vs itself

…and vs the same year elsewhere+0.346q = 0.014 · 59 countries

Year-on-year changes—q = —

Read with care.

Almost all of this indicator's variation is between countries, not within them, so the within-country estimate rests on a small part of the data.

593 country-years (one country in one year), 59 countries, 2000–2022, about 10 years each on average. Share of the variation that happens within countries over time: 9% for Researchers, 5% for Slum share of urban population. The margins of error allow for each country appearing many times, and for each year’s value being close to the year before.

Year-to-year changes are a cautious test, not a final answer. Looking only at changes from one year to the next removes each country’s own trends. But it also makes measurement mistakes louder, which pulls the results toward zero. A near-zero result here is weak evidence of no link, not proof.

With one measure years behind the other

Same year (lag 0): +0.346. A peak away from zero does not show which comes first. These series change slowly — this year’s value is close to last year’s. That makes the curve smooth and nearly symmetric, whatever produced the data. Even a sharp peak at one lag (a gap of some years) would not prove that one measure changes the other.

The data

	per million people	% of urban population	Years
Korea, Rep. KOR	9,472	4.5%	2023, 2022
Sweden SWE	8,911	0.336%	2023, 2022
Denmark DNK	8,838	0%	2023, 2022
Singapore SGP	8,782	0%	2022
Finland FIN	8,315	0%	2023, 2022
Norway NOR	7,451	0%	2023, 2022
Austria AUT	6,634	0.0466%	2023, 2022
Netherlands NLD	6,563	0%	2023, 2022
Switzerland CHE	6,108	0%	2023, 2022
Belgium BEL	5,990	0%	2023, 2022
Portugal PRT	5,983	0.059%	2023, 2022
Iceland ISL	5,953	0%	2023, 2022
Germany DEU	5,926	0%	2023, 2022
Ireland IRL	5,753	8.5%	2023, 2022
Canada CAN	5,624	1.1%	2022

World Bank, World Development Indicators
World Bank, World Development Indicators

Sources

Researchers

Researchers in R&D (per million people)

UNESCO Institute for Statistics · CC BY 4.0 · updated quarterly

Researchers counted as full-time equivalents (two half-time researchers count as one), from national research surveys that many countries run only now and then. So coverage is thin outside the OECD.

Slum share of urban population

Population living in slums (% of urban population)

UN-Habitat · CC BY 4.0 · updated quarterly

How this was computed

Data used: most recent value in 2010-2025; values come from 2010–2024. To adjust for income, each measure is first predicted from GDP per person (in percentage terms, on a log scale) with a straight-line fit. Only what is left over is then compared. This is called a partial correlation. The line is drawn the standard way (ordinary least squares), which picks the line that comes closest to all the countries at once. The error margins allow for countries in the same region resembling each other, using 7 World Bank regions. The q-value corrects for testing all 12,497 pairs at once, using the Benjamini–Hochberg method. Underlying data last updated DYB 2024. How the country data works · explore Researchers and Slum share of urban population

This page shows that two measures go together. It does not show that Researchers changes Slum share of urban population, or the reverse. These figures also describe countries, not individual people. See the ecological fallacy.