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

Across 178 countries the link before adjusting for anything is r = -0.66, on a scale from -1 (opposite) to +1 (in step). A version that uses only each country's rank gives -0.74.

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 +0.153 (129 countries, 1,161 country-years). Using year-to-year changes, it is —.

Does Physicians 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.

Physicians vs. Slum share of urban population

Fades after adjusting for income

Across 178 countries, Physicians and Slum share of urban population rise and fall together at r = -0.66 (on a scale from −1 to +1, where 0 means no link). Comparing only countries with similar income (GDP per person) shrinks it to -0.20, which could easily be chance (q = 0.089, 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: direction is not consistent across regions.

Comparing countries across the middle half of physicians, 0.379 to 3.39 per 1,000 people, slum share of urban population is better by 29.3% of urban population at the top of that range than the bottom. Comparing only countries with similar national income, the gap is 9.87% of urban population.

Link before adjusting (r)-0.661p = 9.5e-24 · 178 countries

After adjusting for national income-0.205p = 0.006 · likely range [-0.34, -0.06]

p, allowing for regions0.015standard error 0.060 · 7 regions

Check for luck (q)0.089across 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.

Physicians · per 1,000 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	-0.661	9.5e-24	178
By rank (Spearman), not adjusted	-0.736	1.3e-31	178
Standard (Pearson), adjusted for national income	-0.205	0.006	178
By rank (Spearman), adjusted for national income	-0.221	0.003	178

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 178 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: +0.456 (a minus sign means it grew).

How solid is it?

Leaving out one country at a time, r ranges from -0.263 (without SYC) to -0.187 (without GNQ). 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: SYC (-0.058).

Fragile: this link may not hold up.

direction is not consistent across regions

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	28	-0.07
Europe & Central Asia	49	-0.17
Latin America & Caribbean	26	-0.09
Middle East, North Africa, Afghanistan & Pakistan	21	-0.18
Sub-Saharan Africa	46	+0.07

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	60	-0.30
Middle third	59	-0.29
Richest third	59	+0.00

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	104	-0.20
Muslims	49	-0.38

By last european coloniser

	n	r
France	25	-0.56
Never a European colony	21	-0.15
Spain	19	-0.30
United Kingdom	57	+0.00

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 = -0.205 after dropping 0 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.

Loading…

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.

Within countries over time, there is no link that is clearly more than chance (r = +0.153, comparing each country only with itself over the years, and each year only with the same year elsewhere). Whatever the cross-country picture shows, countries whose physicians moved did not tend to see their slum share of urban population move with it.

Across countries (adjusted)-0.205for comparison

Within countries-0.129each country vs itself

…and vs the same year elsewhere+0.153q = 0.111 · 129 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.

1,161 country-years (one country in one year), 129 countries, 2000–2022, about 9 years each on average. Share of the variation that happens within countries over time: 8% for Physicians, 7% 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): +0.153. 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 largest value on this curve (+0.27 at lag -9) is higher than the same-year one by 0.12. That gap is not a finding. It is the largest of 21 closely related estimates, and picking the biggest of many tests always makes it look bigger. That is exactly why nothing on this site is ranked or chosen by lag.

The data

	per 1,000 people	% of urban population	Years
Seychelles SYC	6.6	48.7%	2022
Greece GRC	6.58	0.05%	2022, 2012
Portugal PRT	5.85	0.059%	2022
Georgia GEO	5.64	7.08%	2023, 2022
Austria AUT	5.51	0.0466%	2023, 2022
Russian Federation RUS	5.11	2.62%	2022
Argentina ARG	5.11	14.5%	2023, 2022
Andorra AND	5.07	0%	2023, 2022
Norway NOR	4.97	0%	2023, 2022
Belarus BLR	4.72	0.004%	2023, 2019
Uruguay URY	4.67	1.3%	2022
Germany DEU	4.53	0%	2022
Malta MLT	4.51	0.0375%	2022
Denmark DNK	4.5	0%	2021, 2022
Switzerland CHE	4.48	0%	2022

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

Sources

Physicians

Physicians (per 1,000 people)

World Health Organization · CC BY 4.0 · updated quarterly

Reported irregularly, so the latest value in the time window used is from a different year for different countries. Hospital beds, already on the site, have no "better" direction, since more beds is not plainly better. More doctors is closer to plainly better, so a direction is set on that basis.

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 2012–2023. 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 Physicians and Slum share of urban population

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