Although her international standing has nosedived in the latest World Thoroughbred Rankings (WTR), the system is flawed and Black Caviar will be back near the top by year's end, an expert involved in compiling the ratings says.

Racing Victoria's chief handicapper and Australian representative to the 15-nation WTR group, Greg Carpenter, says the current system places Australia's unbeaten champion as 18th on the list due to her performance in the last six months, which does not represent her overall body of work.

The fluctuation in the rankings is confusing, Carpenter says, and he will argue for a system overhaul at the annual rankings meeting in Hong Kong next month.

"I say, 'it confuses people when you drop performances out because they aren't in the last six months, and people can't follow it'," he told AAP.

The main list is published at the end of each calendar year, and takes into account every performance in that year.

Black Caviar's current low rating is due to the narrow margin by which she won her most recent race - the Golden Jubilee Stakes - at Royal Ascot in June.

"She was injured (and) won very narrowly, so her numeric rating from that individual performance is lower that she has achieved in the past," Carpenter said.

The WHR has classified her Black Caviar's peak performance this year as her win in the Lightning Stakes when she beat Haylist to achieve a rating of 130.

"She only narrowly won (at Royal Ascot), her trainer was on the brink of withdrawing her because of injury, (so) it wasn't her highest-rated performance," Carpenter said.

"But others would argue that on the basis of courage, the challenge, it was one of her best performances."

He said the annual rankings, to be released in January, would show a more accurate picture of her overall performance, placing Black Caviar and French horse Cirrus des Aigles in second place with an equal rating of 130.

Recently-retired British superstar Frankel has topped the list all year with a rating of 140.