Why most of the wealth in the world is found in the areas north of the Tropic of Cancer?

I think that most of the wealth in the world is found in the areas north of the Tropic of Cancer because it is not as hot as it is in the areas that are south of the Tropic of Cancer. I think this because the hotter it is, the faster things like flowers wilt from the heat. But in the cold, they still need sun, but it's as if in the cold, they hibernate. So it's good to have a little bit of each. You can find a little bit of each mostly on in the areas north of the Tropic of Cancer. So that means if you have a little bit of each, it can be cool, hot, or snowy but your plants will still survive! The reason why I said this is because farming was a big jump, but in the areas north of the Tropic of Cancer it just seems like a better place to plant you crops because the faster or the longer the crops live, the more food, and the more food the more communities will be found in that place. Making it wealthier.


I also think that the areas north of the Tropic of Cancer are wealthier because the countries there seem to cover more land and they seem to be connected to more land. That helps because the people in them can travel even farther and see more cities along the way.  With more cities to explore that means more trade. The more trade the more items. The more items the more furniture and houses. The more furniture and houses the more communities. The more communities that means the more people in the communities. If you have more people in a community then you would have to have more money to support those people. Because of being able to travel farther distances and get rarer items that means the more wealth you have.

http://www.prb.org/Educators/TeachersGuides/HumanPopulation/PopulationGrowth.aspx

The graph above proves that there has more growth of population in the areas north of the Tropic of Cancer. Asia is a BIG difference the Oceania (Australia) The percents mean the percentage of how many people live in that area in the world. I am NOT saying that Australia is not very wealthy. It's just possibly A LOT healthier. Haven't you noticed that McDonalds is mostly found in areas north of the Tropic of Cancer? Here's a graph to show. The graph proves that is some places, as it may seem, has a easier time domesticating animals like cows that will soon be eaten. Notice on the graph that there are HUGE bubbles mostly found in the areas north of the Tropic of Cancer. Compared to the areas north of the Tropic of Cancer the areas south of it are a lot healthier. And Australia has to be one of the healthiest. WOOHOO AUSTRALIA!!!  It has only around 100-499 McDonalds, while the US has 10,000 and counting!Wait.. I just realized something, this has turned more into a health concept than answering the question, Why most of the wealth in the world is found in the areas north of the Tropic of Cancer? I guess I just got a little bit carried away, hee hee. But the food consuption does also say why America has SO MANY PEOPLE! America needs bigger city thus needing more money. Where do they get it? How do I get a flight to Australia in the next week? (Pretend I never said that)
http://www.princeton.edu/~ina/infographics/starbucks.html