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FINANCIAL HIGHLIGHTS (Per Unit Performance Data and Other Supplemental Financial Data) (Details) - $ / shares | 3 Months Ended
--- | ---
Mar. 31, 2017 | Mar. 31, 2016
Per Share Operating Performance: |  |  |
Net asset value, beginning of period |  | $ 9.29 | $ 8.69
Total income (loss) |  | (1.7) | (2.03)
Total expenses |  | (0.02) | (0.02)
Net increase (decrease) in net asset value |  | (1.72) | (2.05)
Net asset value, end of period |  | $ 7.57 | $ 6.64
Total Return |  | (18.51%) | (23.59%)
Ratios to Average Net Assets |  |  |
Total income (loss) |  | (18.65%) | (23.33%)
Management fees | [1] | 0.60% | 0.60%
Expenses excluding management fees | [1] | 0.73% | 0.62%
Net income (loss) |  | (18.97%) | (23.64%)
[1] | Annualized.

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