The stock market may lose a big tailwind come January (PKW, SPY, SPX, DIA)

Since the financial crisis, S&P 500 companies have spent trillions of dollars buying back shares of their own stock. In the third quarter alone, these companies gobbled up $156 billion worth of themselves. Goldman Sachs' David Kostin estimates that these companies will spend another $608 billion in 2016 buying back shares, up from $568 billion in 2015. It's important to note that these buybacks — which are enormous enough to sway markets — don't occur evenly throughout the year. "Typically, ...