"What we refer to as a “moat” is what other people might call competitive advantage . . . It’s something that differentiates the company from its nearest competitors – either in service or low cost or taste or some other perceived virtue that the product possesses in the mind of the consumer versus the next best alternative . . . There are various kinds of moats. All economic moats are either widening or narrowing – even though you can’t see it." -Warren Buffett (Outstanding Investor Digest, June 30, 1993, via "Measuring the Moat")
