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Going long this ETF is similar to going long the bond's yield, which can be charted by typing $TYX into StockCharts.com:
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Alternatively, if you were bullish on bonds, you could short the inverse ETF, which would fall if bonds rose. A more straight forward option would be to just buy another ETF altogether, TLT, which follows long term treasuries on a one to one basis:
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The reason I bring these ETFs up is that they can provide additional diversification to one's portfolio. For example, in the late part of 2008, this was one of the only markets that was performing well.
Currently, these funds are in sideways trends, but I am waiting patiently for the next trend to emerge.