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FINANCIAL HIGHLIGHTS (Details) - $ / shares | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Per Share Operating Performance: |  |  |
Net asset value, beginning of year | $ 18.18 | $ 15.70 | $ 12.22
Total income (loss) | (2.82) | 2.61 | 3.60
Net expenses | (0.18) | (0.13) | (0.12)
Net increase (decrease) in net asset value | (3.00) | 2.48 | 3.48
Net asset value, end of year | $ 15.18 | $ 18.18 | $ 15.70
Total Return | (16.50%) | 15.80% | 28.48%
Ratios to Average Net Assets |  |  |
Total income (loss) | (14.88%) | 16.22% | 34.23%
Management fees | 0.75% | 0.75% | 0.75%
Total expenses excluding management fees | 0.23% | 0.48% | 0.32%
Expenses waived | (0.08%) | (0.33%) | (0.17%)
Net expenses excluding management fees | 0.15% | 0.15% | 0.15%
Net income (loss) | (15.78%) | 15.32% | 33.33%

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