I ran a sim with SDS from 1999 - 2013. There were numerous realized trades from 1999 onwards. How is this possible when the inception date of SDS was 7/11/2006?
Georg,
Since SDS is based on a defined function of the S&P 500 index, P123 has synthesized it back to 1999 based on that function. P123 has also done that with many ETFs that have a defined function of an index if the index existed back then. Only the price data is synthesized, not the volume. The synthesized data may not be exactly what would have been if the ETFs had been in existence in 1999, but it is good enough to be able to test over a much broader time period that includes 2 recessions than only the ETF’s actual data.
Denny 
Denny,thank you for this comprehensive answer. I thought that something like this was the case, but I just wanted to be certain. I am sure that this is not very well known in the community.
Can we have a list of ETFs that got their timeframe extended? What about USO?
No USO only goes back to 04/10/2006.
Denny