Development is usually banded by income. These bands are set by energy, in gigajoules of primary energy per person per year, because energy is the physical constraint: a country at 20 GJ cannot run OECD healthcare whatever its politics, and a country at 200 GJ can afford to whether or not it does. The tiers place a country by what its throughput makes possible, not by what its GDP suggests.
The four tiers
| Tier | Energy | What it buys |
|---|---|---|
| I. Below the floor | under 30 GJ | Biomass for cooking, intermittent or absent grid, water carried or pumped by hand. Clinics without cold chains. The tier where an infant's odds of surviving the first year are still set by energy rather than medicine. |
| II. Surviving | 30–70 GJ | Electricity that stays on, sanitation, refrigeration, mechanized transport for goods if not for people. Survival outcomes have essentially saturated. Almost nothing else has. |
| III. Building | 70–150 GJ | Cement, steel, rail, universal appliances, climate control, private mobility. A country occupies tier III while it constructs the physical infrastructure it will use for the next 50 years. |
| IV. Developed | 150+ GJ | The infrastructure exists and the energy goes to running and replacing it. Air travel, large vehicles, and the throughput of an economy that has already poured its concrete. |
Where humanity sits
| Tier | Countries | People | Share | Energy | Share | Band mean |
|---|---|---|---|---|---|---|
| I. Below the floor | 48 | 3.52 bn | 44.2% | 59.3 EJ | 9.6% | 16.8 GJ |
| II. Surviving | 20 | 1.20 bn | 15.1% | 60.8 EJ | 9.8% | 50.6 GJ |
| III. Building | 32 | 2.48 bn | 31.1% | 294.0 EJ | 47.4% | 118.7 GJ |
| IV. Developed | 20 | 0.77 bn | 9.6% | 205.9 EJ | 33.2% | 268.6 GJ |
Where the boundaries come from
Only the floor is published. 30 GJ is the highest of the four survival thresholds in R. B. Jackson et al. (2022), Ecosphere 13(4): e3978: electricity access at 12 GJ, basic sanitation at 15 GJ, infant survival at 24 GJ, life expectancy at 30 GJ, across 140 countries. Those are 99th-percentile frontiers — what the best performers achieve at that energy level, not what a typical country gets — and the authors decline to claim causation.
70 GJ and 150 GJ are this publication's construction. Gapminder, Smil, the saturation literature and the decent-living-energy literature map no development tier to gigajoules per capita, and the saturation literature could not supply these: its highest threshold of any kind is 125 GJ, and its finding is that outcomes saturate early. 70 GJ separates countries that ration energy from countries that build with it, and sits a little above Thailand and Brazil and a little below Turkey. 150 GJ separates countries still accumulating physical stock from those maintaining it, above Germany, Japan and Malaysia and below Korea, Australia and Russia.
Placing a country
- Take primary energy per person per year, on the substitution method, and read the band. Not final energy and not electricity — the tiers are set on primary throughput.
- A national average hides a country's own tier I. Measured on individuals rather than country means, 38% of people consume under 10 GJ against the 8% a national-average reading would give (Oswald, Owen & Steinberger 2020, Nature Energy 5, 231–239). That figure is a household final-energy footprint, roughly half the size of the primary energy used here and on a different basis, so it is not comparable directly; the usable finding is the direction and order of magnitude of the country-average bias. Nigeria has people in every tier, and so does India.
- The tier is a ceiling, not a verdict. It says what the throughput makes possible. Whether a country delivers it, and to how many, is a question of governance.
Technical notes
- Basis. Primary energy per person per year, substitution method, which counts one joule of solar electricity as 2.44. On a final-energy basis the same countries sit lower and the boundaries do not transfer.
- Relation to Rosling's levels. Rosling banded income, at roughly $2, $8 and $32 a day. These are the same idea moved onto Smil's unit. They are not convertible: energy intensity across 30 large economies runs from 0.80 to 8.38 GJ per $1,000 of PPP GDP, a factor of 10.5.
- Sensitivity. Moving the middle boundary from 70 to 60 GJ shifts roughly 0.2 bn people up a band; to 80 GJ, roughly 0.1 bn down. Moving the top boundary anywhere between 140 and 160 GJ moves fewer than 0.1 bn. Nothing here depends on either to the nearest ten gigajoules.