However, one thing I keep seeing mentioned is that the Boston course, sans strong tailwind, is unaided despite the elevation loss due to the uphills positioned near the end as they are. I am unsure why this gets accepted as fact so easily without any strong analysis of evidence that I have ever seen. The main supporting arguments I see forwarded have been along the lines of “if you think the elevation loss is an aid then why has the WR not been bettered there before?” (well, race tactics + lack of pacers, chiefly) or “it looks like an aid to most people until they have to run it and find out what the hills do to your legs” (offered often seemingly by the type to let the early downhills pull them out faster than is wise). Sort of circular logic, an amalgamation of anecdotal bias that disregards context to some degree. Sure, there are factors like headwind and/or heat/humidity that would render a WR essentially impossible on the course, but those would significantly negatively affect the odds of a WR at Berlin, Chicago, London, or Rotterdam, as well. It still seems highly likely that anyone who prepares for the specifics of the course, executes the right strategy for that course, and gets favorable enough weather on race day (weather that would be favorable enough at any other marathon) should be able to run their best time there.