From the article: >40 per cent of the world's 8.2 billion people live in rural areas >the rural population is underestimated by half Based on the first state

From the article: >40 per cent of the world's 8.2 billion people live in rural areas >the rural population is underestimated by half Based on the first statement: 8.2*0.4=3.28 billion rural globally; And according to the second statement, there re actually twice as many, so another 3.28 billion people, or: 8.2+3.28=over 11 billion in total on Earth.