Since kicking off its share buyback (or repurchase) program in 2013, Apple has spent $327 billion until 2019 to buy back 2.5 billion shares at an average price of $131 per share. It repurchased its shares worth US $ 23 billion in 2013, $ 45 billion in 2014, $36 billion in 2015, $ 29 billion in 2016, $ 33 billion in 2017, $ 73 billion in 2018 and $ 67 billion in 2019. The pickup in Apples buyback pace in 2018 and 2019 was due to U.S. tax reform and Apple utilizing cash that had been in non-U.S. subsidiaries. To put that total ($ 327 billion) in perspective, its more than the market capitalization of 85% of the companies in the S&P 500 index of the US

Please analyze share buyback (or repurchase) behaviour of Apple (going by the share repurchase history of the company furnished in Appendix 2) in view of the various theories of share buyback.