"Well, I guess you're right, IGR isn't underperforming SLR and NST. Why then are they up 50% and 150% while IGR is down slightly from a year ago?"
I think Moorookamick partly answers that question in his second para.
SLR may have performed better over the past 12 months but there is no way I would swap my IGR holding for the equivalent holding of SLR at this point in time.