Which of the factors explains most of the differences in standards of living among countries around the world?

The factor that explains most of the difference in standards of living among countries around the world is PRODUCTIVITY.
One major measure that can be used to determine the standard of living of people in a particular country is the growth rate of the its Gross Domestic Product [GDP] per capita. The growth rate of GDP is a reflection of the labour productivity of that country. Labour productivity refers to the measurement of the amount of goods and services that are produced in a country by one hour of labour. An increase in productivity signifies an increase in the standard of living of the people in the country. Labour productivity differs from one country to another and this result in difference in the standard of living.