I am aware that ATS is one of the largest holdings in your Growth Portfolio and it's one of your favorites. Thank you for your invaluable service !!
If there is no material public information, insider trading, broker reports or other news then we are typically at a loss to explain stock movements. As you know, stocks do not always move rationally. The problem here is any answer (in the absence of hard news) is only an assumption. As such, it could be right, or not even close. It is one reason why it is better to look at longer trends, because the 'reasons' for shorter term moves are often simply not there. When yields rise growth stocks do get hit, and this has been happening more or less since early August, as bond yields have risen farther than expected. But we would argue with the 'failure to participate in rallies' point. ATS is massively ahead of the TSX this year, up 30%. It's up 157% over five years.