World population in 2015 = 7.3 billion
Worldwide average life expectancy in years = 71 (men 69; women 73)
Worldwide average gross income (before taxes) per person per year = $15030 (developed countries $39020; underdeveloped countries $2270)
Note that these averages are skewed by the incomes of the ultra-rich persons. The median incomes are much lower. You have to see the distribution of incomes to appreciate this statistical fact.
source for the data shown above: http://www.prb.org/pdf15/2015-world-population-data-sheet_eng.pdf
World population estimates from 1800 to 2100, based on “high”, “medium” and “low” United Nations projections in 2010 (colored red, orange and green) and US Census Bureau historical estimates (in black). Actual recorded population figures (as of 2010) are colored in blue. According to the highest estimate, the world population may rise to 16 billion by 2100; according to the lowest estimate, it may decline to 6 billion.
You should also check out the application from www.census.gov that produces summaries for all countries