Hans Rosling 200 countries, 200 years, 4 minutes

Here is Hans Rosling's 200 countries and 200 years in four minutes. Here are some questions from the four minutes.

What does the x axis represent?
Are the x axis numbers linearly larger? (This question was addressed in class.)
What does the y axis represent?
Are the y axis numbers linearly larger? (This question was addressed in class.)
What does the color of a dot represent?
What does the size of a dot represent?
Which continent has the most countries getting healthier and wealthier in the 19th Century, due in large part to the Industrial Revolution?
Rosling stops for a pair of global catastrophes that overlapped in time. What are they?
At the end of World War II, what country is in the lead in terms of health and wealth?
In 2009, what country is in the lead in terms of health and wealth?
In 2009, what country is far behind in terms of health and wealth?
When splitting up China, Shanghai is about on par with ______ while rural parts of Guizhou are on par with _____.

Watch the video and answer the questions. The video doesn't fit the screen very well, so click on it and watch it on YouTube.
(Answers in the comments.)