Soros Fund Management has doubled up a bet that the S&P 500 SPX is headed for a fall. Within Friday’s 13F filings news was the revelation that the firm, founded by legendary investor George Soros, increased a put position on the S&P 500 ETF by a whopping 154% in the fourth quarter, compared with the third. (A put or short position basically gives the owner the right to sell a security at a set price for a limited time, and in making such a bet, an investor generally believes the security is going to decline.) The value of that holding, the biggest position in the fund, has risen to $1.3 billion from around $470 ... (full story)