Why do countries GDP DIFFER?

GDP REVIEW Gross Domestic Product shows us how well or poor a country is doing economically. It measures the total value of goods and services that are produced in a country in a year GDP per capita is the total income of a country divided by the number of people who live in that country. It shows how much people make on average at work.

Canada United States Niger Germany Country size 9,984,670 sq km 9,833,517 sq km 1.267 million sq km   357,022 sq km  Population 35,881,659 329,256,465 19,866,231 80,457,737 Natural resources Bauxite (makes aluminum), iron ore, nickel (coins, pipes and batteries),zinc (batteries, plastic), copper (wiring, car motors), gold, lead (car batteries, weights for lifting, ammunition, paint), rare earth minerals, molybdenum (missile and aircraft parts, nuclear power industry), potash (fertilizer in agriculture and soap), silver, wildlife, hydropower, fish, timber, oil, coal, diamonds- 19 total coal, copper, lead, molybdenum, phosphates (fertilizer and animal feed supplements), rare earth elements, uranium (nuclear power plants and weapons), bauxite, gold, iron, mercury, nickel, potash, silver, tungsten, zinc, petroleum, natural gas, timber, arable land, note, the US has the world's largest coal reserves with 491 billion short tons accounting for 27% of the world's total-20 total uranium, coal, iron ore, tin, phosphates, gold, molybdenum, gypsum, salt, oil-10 total coal, lignite(type of coal used for steam powered industries), natural gas, iron ore, copper, nickel, uranium, potash, salt, construction materials, timber, arable land-12 total  Arable land 4.7% 16.8% 12.3% 34.1% urbanization 81.4% 82.3% 16.4% 77.3 Physician Density 2.5 doctors/1000 2.57/1000 .02 doctors/1000 4.19/1000 Life expectancy 82 years 80.1 years 56.3 years 80.9 years Literacy Rates 99% 19.1% School life expectancy 16 years 17 years 5 years 17 years  GDP per capita $48,400 $59,800 $1,200 $50,800

What Accounts for the differences in GDP?