MPD is actually a hybrid indicator and the reasons for it being low can range from high drops due to any hardware / parameter / frequency / neighbour / transcoder issue. or low traffic.
Would depend on What the the DCR / Traffic and the morphology of the region.
@Pix just to add to MPD discription.
it should be Traffic * Granuality / Drops. like for 60 minutes granuality it should be Traffic * 60 /Drops . Is an excellent hybid particularly usfull to benchmark redesigns, as chances of traffic loss/ gain and changes in Drops so if MPD increases then all is towards good if decreases then all is deteriorating… and Alcatel doesn’t normally use it…
@ KJB: @ the things that can increase traffic i.e improve CSSR / reduce blocking and decrease drops like adding missing neighbour. optimal traffic distribution etc would add to MPD. Also try redesigns they are good at this.. which vendor are you using, I could then give some vendor specific advise if I have worked on that.
@ Pix: the threshold is variable for Urban Suburban it is very good normally in range to 150,200 and above, for RR its close to 100 and for extreme remote it can be even below 50.. but all depends on the Quality from where the cell is taking calls like overshootings trains etc.