Is the degradation of trend following performance a cohort effect, instrument decay, or an environmental problem?

It's probably bad luck to say this, but the most recent poor performance of CTAs and trend following managers this year appears to have been reversed. My own system is up over 12% since the nadir of the summer drawdown, and is now up for year; admittedly by only by 5.5%. Nevetheless, it's true to say that trend following performance appears to have been degrading over the last few decades. If I…