Improvement of individual athletes in a decathlon

Inspired by Janek's blog about "how good competitors in Götzis actually were" a question occurred to me:

what is the biggest improvement of his PB that a decathlete has ever achieved in a competition?


I just started asking myself that as I remembered Andrei Krauchanka in Götzis 2007 smashing his PB by 604 points or also Eelco Sintnicolaas in Götzis 2009 (improved by 545 points) and I wondered if there have ever been similar improvements of PBs

I suppose it's quite hard to answer that question, as you have to decide what you want to choose as the athletes first actual PB. And you might get quite huge improvements in the beginning of an athlete's career.

So I hope someone else might also be interested in that topic and suggest some ways to solve it