Drawing upon previous articles, I think the main points for trying to assess long-term performance upon DVRs (rather than MVRs) are as follows:  

1. virtually all investment performance based on market values
2. pension trustees have very long timeframe
3. trustees are not unduly constrained by short-term results
4. short-term results untrustworthy (Joseph effect)
5. relying on market values can give wrong long-term message
6. "broadly right" better than "precisely wrong"
7. trustees must monitor what delegated managers are doing
8. any investment strategy bears associated risks (future unknown)
9. seven types of risk briefly defined
10. how can trustees balance return against risk?
11. US definition (price volatility) irrelevant to trustees
12. DVR is more robust and less subjective than might be thought