What are the constituents of the UltraShort ETF (ticker: SDS)?

Question

The ProShares UltraShort ETF seeks daily returns equal to twice the inverse of the performance of the S&P 500. What positions do the managers take to emulate this performance?

Answer 1

I assume it's futures and swaps, collateralized by T-bills or some other short-term notes.  That's what most of them do.

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