This is an adaptation of the motion chart in Mike Bostock's The Wealth and Health of Nations that dynamically adds text labels for countries that have interesting-looking movements. As in the original, you can either just watch the animation, or move your mouse over the year to go back or forward in time.
The idea is that a dot with a dramatic movement should automatically get a label, so that the user does not need to interact in order to find out which country it represents. To figure this out, I preprocess the data to measure the amount of movement of each country in a time window, and show labels for the countries whose movement is above a certain threshold (capping at a maximum of 5 labels visible at a time, with larger dots getting priority).
I used updated data (to 2015) from the original source, Gapminder, and chose to start the animation later (in 1865 instead of 1800) because not much happens in the earliest years.