By Nico Willson for Kapitall. Over the past 12 months more than $500 billion has been spent repurchasing shares of US stocks. Apple (AAPL), Walmart (WMT), IBM (IBM), Exxon (XOM) all have extensive buyback schemes. IBM spends twice as much on share repurchases as on R&D, while Exxon has spent over $200 billion buying back shares, enough to approach the buybacks by rival BP (BP). The trend has even spread beyond the US to more conservative corporate cultures, like Japan, where companies are buying back record amounts of shares, led by Toyota (TM) and Mitsubishi. Buybacks return surplus cash to their shareholders in a similar manner to paying out dividends. If the firm sees little opportunity for other investment, giving back to investors is a good thing to do because it helps support a higher price for the shares. But does it also reflect poor growth prospects? It's hard to say. The announcement of a buyback scheme often sees a spike in share price and quick profits for short-term investors. However, if buybacks are overdone and share prices artificially supported, they will, at some point, topple. According to an analysis by Barclays, companies with the biggest buy-back programs by dollar revenue have outperformed the broader market by 20% since 2008. Jonathan Glionna, head of U.S. equity strategy at Barclays said: "There are a couple of reasons why companies do buy-backs. One is that it seems to work; it makes stocks go up." Apple is the biggest buyer of its own stock with $32.9 billion spent. IBM is second with $8.2 billion spent repurchasing 45.2 million shares in the first quarter of 2014. The company itself was the buyer, holding 13% of all IBM shares that changed hands that quarter. Exxon Mobil is another big buyer with $13.2 billion spent on its stock in the first quarter of 2014. According to FactSet, over the past year Apple stock has shot up 54%, IBM stock is down 0.2% and Exxon Mobil has increased 8.5%, compared with a 13% increase in the S&P 500. Are buy-backs only a short-term strategy? Use the information below to begin your own analysis and let us know what you think in the comments.