Investors should follow and learn from these two dominant businesses. Investing is often done best when it's kept simple. For the average person out there looking to boost their portfolio returns, this could mean putting on your customer hat and finding businesses that you already deal with. Not only does this allow you to lean on your own first-hand experience, but it limits the universe to companies that you probably understand very well. This will undoubtedly lead you to the retail sector, which is extre ...