Wind and solar aren't the only resources that can be curtailed.  For each interval in the 60 day disclosure report CIM View looks at the offer curves and limits for each resource and compares the MWs that would be dispatched at the average ERCOT price (System Lambda) to the MWs that would be dispatched at the LMP for that Resource Node.  If the System Lambda MWs are higher, well, there's your curtailment.  We've got this data going back on a per resource level for more than the last three years.  Contact us if you want to see which resources are getting curtailed the most.