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FINANCIAL HIGHLIGHTS (Details) - $ / shares | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Per Share Operating Performance: |  |  |
Net asset value, beginning of period | $ 22.95 | $ 17.82 | $ 21.05
Total income (loss) | (5.59) | 5.32 | (3.04)
Total expenses | (0.13) | (0.19) | (0.19)
Net increase (decrease) in net asset value | (5.72) | 5.13 | (3.23)
Net asset value, end of period | $ 17.23 | $ 22.95 | $ 17.82
Total Return | (24.92%) | 28.79% | (15.34%)
Ratios to Average Net Assets |  |  |
Total income (loss) | 61.24% | 26.56% | (6.16%)
Management fees | 0.60% | 0.60% | 0.60%
Expenses excluding management fees | 0.28% | 0.28% | 0.22%
Net income (loss) | 60.36% | 25.68% | (6.98%)

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