Karsten's impressive CV in economics and monetary policy doesn't mean he's immune to hubris. Every analysis needs to make choices about how to treat historical data and how to model the future
And he explains every single choice specifically and provides his exact reasoning for why he did it and why that is appropriate for the specific analysis question he is answering. I suspect you are skimming over his reasoning too quickly to evaluate whether it is valid or not, and likely applying some confirmation bias because you don't like his conclusions (likely being more critical of anti-RP content than pro-RP content).
His CV is the reason he has the background to know what types of adjustments are required to isolate different effects (considerations that do not come naturally to non-economists), because a lot of the social media financial claims conflate multiple things together that require disentangling to get unambiguous results.
I urge you to slow down on the assumptions of bias on his part and consider his deep expertise in this area gives him a background in knowing when raw economic data doesn't say what it appears to say without adjustments. Each individual adjustment/choice should be evaluated on it's own merits, and unless/until you find specific biased choices, challenge him (in blog comments) specifically on why you believe they are biased or invalid and see how he responds (he responds within a day or two to most comments), everything you're saying here is pure speculation.
Karsten's baseline dislike of risk parity and SCV colors his choices. He manipulates the parameters to such a degree that IMO his conclusions are not meaningful. He tosses out historical data if it doesn't align with what he has decided the future will look like, and he uses overly pessimistic forecasting assumptions for assets he disfavors.
I disagree on all counts. You are entitled to your opinion of course, but everything you said above is only an opinion, and mostly your speculation of Karsten's motivations, rather than his actual demonstrated behaviors.
He is extremely transparent with his assumptions and reasoning for making adjustments to data sets, and he is open to criticism. If he weren't, he wouldn't leave his blog comments section unmoderated, and open indefinitely (all the way back to part 1).
Karsten himself concluded in 2020 in part 34 of his SWR series that 10-15% gold improves the SWR of a retirement portfolio. Why has he not incorporated this asset into his recommendations? Why is he still pushing 75/25 six years later?
He has on a few occasions said you can add 10-15% gold if you like and it may increase SWR. He doesn't hide this conclusion, and sometimes brings it up on his own.
As to why he doesn't change his vanilla retirement portfolio recommendation to be 60% stock/25% bond/15% gold, you could ask him, but his ambivalence may be because gold has such a short market price trading history compared to the other asset classes in his datasets (fixed price, illegal to trade for large periods) that his confidence in that conclusion may be lower than in most of his other research. He has said on occasion that 75% stock / 25% bonds is good enough for most retirees, so it may also be the KISS principle. But again, you could certainly ask him or ask AI - I found it gave a fairly comprehensive answer on Karsten's stated reasoning aggregated from multiple responses he has given.
He recognizes his own biases but follows the data where it leads despite them, as any good researcher would, as evidenced by (from part 34):
with a little bit of confirmation bias, I set out to prove that gold has no place in a retirement portfolio. The average return over time is simply too low. But gold shines (pardon the pun) when all the other asset classes are hurting. And that’s a huge benefit!
