The story of the 20th century was of remarkable average income growth, but it is also quite obvious that the progress was not evenly dispersed. The gaps between rich and poor countries, and rich and poor people within countries, have grown. The richest quarter of the world’s population saw its per capita GDP increase nearly six-fold during the century, while the poorest quarter experienced less than a three-fold increase (Chart 1b). Income inequality has clearly increased. But, as noted below, per capita GDP does not tell the whole story (see section IV).