I probably did not write correctly. And sorry for the useless.
The question was whether you can trust a strategy that ran sideways in the backtest for many years until 2016 and then is rising.
As an example, a simple strategy was chosen to illustrate. Please excuse, there are also other strategies that 2016 resp. until 2018 show a “break”. Compare original Pathfinder strategy attached.
The question I actually wanted to pursue, where does this break come from? Are there any explanations? Should we backtest from 2016/2018 or should we backtest as far as the history goes?
Approaches that I have read say both. But the explanation is pending. For me is a question of trust in a strategy.
Should i just accept it or investigate it?