Investment is the practice of hiding money in one's vest to smuggle it across borders. It originated in the early 1800s when Napoleon needed to smuggle money into Russia to prepare his assault. He decided to send people into Russia with vests stuffed with 100 dollar bills, smuggling a total of 1297200 francs.
By 1900, several strategies were in existence to combat investment.
The Weight Test
This test involves weighing the person's vest against a "control" vest. If the vest is heavier, it has money in it. However, this technique failed miserably because all vests have different weights. So, this technique eventually gave way to:
This technique involves taking everyone's vests before they cross the border, and giving them a random vest, so you have a very low chance of retaining the vest with the money in it. This also failed because hobos with very crappy vests would cross borders in hopes of getting a very good vest in place of their own.
This technique involves hiring a kitten huffer to huff a kitten. The kitten's response will tell you if the vest is legitimate or not. This was not very accurate because kittens don't know what's in a vest. There is anecdotal evidence that Cow huffing works better, but cows were too expensive.
By far the best way to figure out if the vest is legitimate. It involves looking at the stars and planets for the answer. Take a photograph of the night sky and get your 3-year-old to play connect the dots with it. It always forms the word yes or no, and in one or two cases, maybe.
The Stock Market
These days, for efficiency, instead of money being hidden in vests, pieces of paper called stocks are. Each stock can be worth from 500 to 999999999999999999999999999999999999999999999999999999999 dollars. Stocks are sold on the stock market, which is run by a bunch of monkeys.