How many is too many? One
I don't have the figures to hand for NZ, but the stats for the UK have flying on a par with Motorcycle riding for fatalities. The big difference is that for motorcyclists, many of the accidents are other peoples fault, where as for flying...........
I seriously doubt if NZ has any bigger problem than Oz / UK / Eire for accidents where GA is concerned.
Flying remains an inherently safe, but extraordinarily unforgiving passtime.