The pictogram above represents the total population.
If applied to UK, each square of the graph paper represents 1000 people.
If applied to USA, each square of the graph paper represents 2500 people.
Most people, the 60% to the left of the pictogram, do not experience acid reflux but 40% do.
Of those, half (about 20% of the population) experience it frequently, when it;s known as GERD.
Of those with GERD (although some claim not to have felt it), some will develop Barrett's.
The column on the right shows all those with Barrett's (about 5% of the population).
Most people with Barrett's do not know it. Those who do are represented by green squares.
Some will die of esophageal adenocarcinoma. They are represented by red squares.
Although shown as separate groups, it is possible that some who know they have Barrett's may die from the cancer but surveillance and medication reduce that risk.