GDP per capital by country, case study

Countries with small populations will have large sample variances, whereas countries with large population will have much smaller sample variances. There is a Ted talk on this, but I had not found the original video. I only remember it is from a population geneticist.

SEM = sigma / sqrt(sample_size)

R code for demo

world = rnorm(7.1E3)  #world population 7.1 billion
china = sample(world, 1.1E3)  #china 1.1 billion
c1 = sample(world, 20) #20 million pop for country c1

itr = 100
list.china = numeric(itr)
list.c1 = numeric(itr) 
for( i in 1:itr){
 list.china[i] = mean( sample(world, 1.1E3) )
 list.c1[i] = mean(sample(world, 20)  )
}


Reference: 

http://ablog.typepad.com/keytrendsinglobalisation/2013/05/only-30-of-the-world-now-has-a-higher-gdp-per-capita-than-china.html

Ted video on GDP per capital by country.