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FINANCIAL HIGHLIGHTS (Details) - $ / shares | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Per Share Operating Performance: |  |  |
Net asset value, beginning of year | $ 17.82 | $ 21.05 | $ 20.39
Total income (loss) | 5.32 | (3.04) | 0.82
Total expenses | (0.19) | (0.19) | (0.16)
Net increase (decrease) in net asset value | 5.13 | (3.23) | 0.66
Net asset value, end of year | $ 22.95 | $ 17.82 | $ 21.05
Total Return | 28.79% | (15.34%) | 3.24%
Ratios to Average Net Assets |  |  |
Total income (loss) | 26.56% | (6.16%) | 2.46%
Management fees | 0.60% | 0.60% | 0.60%
Expenses excluding management fees | 0.28% | 0.22% | 0.26%
Net income (loss) | 25.68% | (6.98%) | 1.60%

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