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CONTRACTS AND AGREEMENTS - Brokerage Commissions (Details) - USD ($) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Long Duration Contracts Assumptions By Product And Guarantee [Line Items] |  |  |  |
Brokerage commissions | $ 1,985 | $ 2,645 | $ 3,857 | $ 3,219
Brokerage commissions as a percentage of average daily net assets | 0.01% | 0.01% | 0.01% | 0.01%
Rebalancing Investments Transaction [Member] |  |  |  |
Long Duration Contracts Assumptions By Product And Guarantee [Line Items] |  |  |  |
Brokerage commissions |  |  | $ 3,446 | $ 2,439
Brokerage commissions as a percentage of average daily net assets | 89.34% | 75.77% | 89.34% | 75.77%
Trades Necessitated By Creation And Redemption Activity [Member] |  |  |  |
Long Duration Contracts Assumptions By Product And Guarantee [Line Items] |  |  |  |
Brokerage commissions |  |  | $ 411 | $ 780
Brokerage commissions as a percentage of average daily net assets | 10.66% | 24.23% | 10.66% | 24.23%

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