Definition
Income Levels is Rosling's four-band model that places every person on Earth somewhere on a $1 / $4 / $16 / $64-a-day scale rather than into the binary developed-vs-developing slot.
The bands are logarithmic: each step quadruples spending power, which roughly corresponds to a visible jump in housing, transport, food, and schooling. Around 1 billion people live at Level 1, 3 billion at Level 2, 2 billion at Level 3, and 1 billion at Level 4.
Why it matters
How it works
Level 1 (about $1/day) means barefoot walking, fetching water by hand, cooking over an open fire, and children sometimes going to bed hungry. Level 2 (about $4/day) adds a bicycle, a gas canister, a mattress, and primary schooling. Level 3 (about $16/day) brings cold running water, motorbike transport, refrigeration, and secondary school. Level 4 (about $64/day) is hot water at the tap, a car, restaurant meals, and twelve-plus years of schooling.
The amounts are PPP-adjusted daily spending per person, so the same level looks broadly the same in Bangladesh, Bolivia, or Burundi — the material kit is what defines the level, not the flag overhead. This is why pictures of life on each level cluster more by income than by continent.
The historical trajectory is the headline: in 1800 almost everyone was on Level 1; today the majority of humans are on Levels 2 and 3, with the population pyramid shifting steadily upward each decade.