WORLD GDP per capita - step three
Each of the incremental increases in GDP at $2,000 increments were then added by populations. For example, countries and populations from $128 (Somalia) to $1,837 (Solomon Islands) totaled 2,725,625,971---30 countries. And the level from $38,000 to $40,000 totaled a population of 133,357,315 (New Zealand, United Kingdom and France).
Each of these GDP per capita population categories are then converted to square size for the "canvas". The total area for 7 billion population is depicted in 4'x6' feet (3456 sq. in.). So if the first level of 0-$2,000 has a population of over 2.7 billion the canvas square is 36.66 inch representation or 39% of global population (.39 x 2.7 billion). Level $34,000 to $36,000 with 60,917,978 will have a square of 5.48 inches or about 1%.
We now factor in each square, GDP per capita levels. A $2,000 increment will add 1/4 of an inch in depth. For example level $50,000 to $52,000 will have a block thickness of 6.5 inches.
This linked chart should clarify the math.