Okay, you've asked some good questions, but in order to really answer any in true I would need to explain to you parts of economics in far more detail than I am willing to.
Principles of Economics, by N. Gregory Mankiw
If you really want a clear grasp of economics, of why the formulas like PCI make sense when comparing the wealth of two nations, you should read that book.
Reaperzwei wrote...
I'm curious how do the people in government know whats in high demand?
Statistics that they collect from information and clandestine service agencies along with the mandatory reports that companies within their nation must file.
Reaperzwei wrote...
Also you realize that subsidizing anything is just taking money from someone and giving to whoever the government favors at the time.
The government takes subsidies directly out of it's budget, it ends up being funded with taxes in most nations.
It depends on the market of the state, in a privatized market the government will subsidize a company within an industrial or service sector to promote growth; creating jobs, allowing for more exports, balancing imports and generally improving the economic prosperity of the nation. The company will often have a contractual obligation to fulfill a specific task, in the case of Canada we had a few companies build up the oil industry within the tar sands. In a public sector the government has full control over the way the subsidy will be spent; though like I said previously it's not all black and white, some sectors have varying degrees of privatization.