Group endpoint, historical data for new patients

[Lightbeam Development]

Hello,

I have a question about how the group endpoint works using the _since parameter.  We are pulling data weekly using _since and passing in the last date we pulled as _since.  How does this work with new patients added to the ACO?  I would expect to get the historical data for new ACO patients even when using _since, but this isn't what we are seeing.  If this is the case, how should I handle making sure I get the historical data for newly attributed patients?

Thanks!

Lb