Eljay ,these are not 'normal' races which could be scraped or dickered with thru dismal acceptances.
These are special races administered thru the NZ Sires Stakes Board so they are planned well in advance as the eligible horses have paid into them as foals or yearlings with sustaining payments.Payments range from $100 as foal up to $600 for all series payments.So the breeders /owners who make these payments are aware these planned races will be held.
There are a number of Heat races from Southland to Auckland ,with the high stake final later in season.
These races can't be 'scraped' ...the money is 'in the bank'.
There are separate series for males and fillies for the pacers.
The trotters are unisex....no separation !
Generally connections want the separation , they don't want their young fillies having to race the boys .......but the trotters have no choice !!
Dunno what the %'s are , but discussing it with a couple of mates our experiences with young horses has been that less than 20% of horses get to race as 2 year olds[often as late 2 yr olds] so the % would be much lower at this time.....mid January !Among our group we currently involved in some 20 x 2 yr olds and only ONE been to the trials !