American Express (NYSE:AXP) has outperformed the market over the past 15 years by 2.52% on an annualized basis producing an average annual return of 14.02%. Currently, American Express has a market capitalization of $165.64 billion. Buying $1000 In AXP: If an investor had bought $1000 of AXP stock 15 years ago, it would be worth $7,203.46 today based on a price of $233.00 for AXP at the time of writing. American Express’s Performance Over Last 15 YearsFinally — what’s the point of all this? The key insight to take from this article is to note how much of a difference compounded returns can ma…