Why is silicon an important element economically?
It is very useful for technology.
I don't know if you have heard of silicon valley or not, but just in case you haven't, here's a quick definition: Silicon valley is an area of land in America where some of the best businesses involved in technology are based in.
The reason for this is the easy supply of silicon, it is VERY abundant naturally. It is also used very commonly in technology, don't ask where or how, I don't know and its not really important.
Without silicon you probably won't be on your computer, phone, etc right now.