Following Carl Icahn and other investors requests, Apple expanded its buyback program to $90 billion from $60 billion because it views its shares as undervalued. In Q4 2014 only, Apple spent not less than $17 billion on stock buybacks,a 240% year-over-year increase that marks the second-highest dollar amount spent on buybacks during a quarter by any individual company in the S&P 500 since 2005.

When that sum was revealed in October, it was estimated that Apple had already spent $45 billion on repurchasing stock in fiscal 2014. Apple has been the biggest buyback spender of 2014 among the S&P 500. Indeed, Apple has spent about $56 billion to repurchase its stock from fleeing investors at incredible discounts. The amount spent by Apple well exceeded second-place S&P 500 finisher IBM Corp, which used $19.2 billion on buybacks.

The basic logic of a share repurchase is that it returns some of a company’s cash back to its owners. Unlike a dividend, in which a company just writes a check to shareholders, the return of cash is indirect. But by reducing the number of shares outstanding among which a company’s earnings and assets have to divided, a buybacks can increase the value of each share.

Based on Apple’s current annual schedule, the company would likely revisit its buyback efforts once again, following its March 2015 quarter..