You can always find rotten performers in the mutual fund marketplace, but it's rare when you find one that has destroyed vast amount of wealth over a long period of time — and especially when the fund isn't a stock fund.
The fund in question here: Proshares Ultrashort 20+ Year Treasury (ticker: TBT), which has fallen 68.8% the past five years. The fund bets against falling long-term interest rates — and therefore higher bond prices.
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Short funds are typically small trading vehicles. But TBT has $4.1 billion in assets, up from $3.6 billion five years ago. Despite its wretched record, the fund has had net new inflows of nearly $3 billion the past five years.