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FINANCIAL HIGHLIGHTS (Per Unit Performance Data and Other Supplemental Financial Data) (Details) - $ / shares | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Per Share Operating Performance: |  |  |
Net asset value, beginning of year | $ 13.69 | $ 18.32 | $ 17.23
Total income (loss) | (3.86) | (4.33) | 1.32
Net expenses | (0.11) | (0.30) | (0.23)
Net increase (decrease) in net asset value | (3.97) | (4.63) | 1.09
Net asset value, end of year | $ 9.72 | $ 13.69 | $ 18.32
Total Return | (29.00%) | (25.27%) | 6.33%
Ratios to Average Net Assets |  |  |
Total income (loss) | (27.80%) | (19.76%) | 13.23%
Management fees | 0.75% | 0.75% | 0.75%
Total expenses excluding management fees | 0.71% | 0.85% | 0.51%
Expenses waived | (0.56%) | (0.67%) | (0.30%)
Net expenses excluding management fees | 0.15% | 0.18% | 0.21%
Net income (loss) | (28.70%) | (20.70%) | 12.27%

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