“As Aaron Levie, the founder of the online file storage company Box noted in a tweet in 2014, “Sizing the market for a disruptor based on an incumbent’s market is like sizing a car industry off how many horses there were in 1910.” The other factor that can lead to underestimating a market is neglecting to account for expanding into additional markets. Amazon began as Amazon Books, the “Earth’s Biggest Bookstore.” But Jeff Bezos always intended for bookselling to serve as a beachhead from which Amazon could expand outward to encompass his massive vision of “the everything store.” Today, Amazon dominates the bookselling industry, but thanks to relentless market expansion, book sales represent less than 7 percent of Amazon’s total sales. The same effect can be seen in the financial results of Apple. In the first quarter of 2017, Apple generated $ 7.2 billion from the sale of personal computers, a category the company pioneered and once dominated. That’s a great number to be sure, but, over that same financial quarter, Apple’s total revenue was a whopping $ 78.4 billion, which meant that Apple’s original market accounted for less than 10 percent of its total sales.”