Let's imagine that the UN elected you to operate a census and mandated that every living person line up and march past you in single file. How long will you be counting? Simple arithmetic, right?
The world's population is about 7.4 billion. If we figure that each person will take 1 meter of space then the line will stretch 7.4 million KM. The earths circumference is 40,075 KM so the line will stretch around the earth nearly 185 times. The average person walks at about 5 KM/hour therefore 5000 people will pass by you each hour. To make things simple we will assume that you are permitted no breaks and you must work 24 hours per day. In this way you will be able to count 120,000 persons per day, or 43.8 million people per year. It would take you nearly 170 years to count 7.4 billion people.
But I now must throw a monkey wrench into the works. At least at current fertility rates, 135 million people will be born each year. Sadly your counting rate is only about a third of that. The line would never grow shorter - quite the opposite. Each year it would stretch two more times around the earth. So, after 170 years of counting, the line would have grown from 185 laps around the earth to somewhere around 500. Perhaps if everyone sprinted...
Here at Poodwaddle.com we try to use more efficient ways to count people.