[jcranmer]

Cellphone use has gone from basically nothing to ubiquitous in the US from ~1995 to 2015, with a particularly steep incline in the middle of that range (2000-2005 is when I'd estimate the biggest increase was). With more or less of a lag depending on how well-developed a country is, this is also true for most of the world--even in poor, underdeveloped countries, cellphone use is pretty damn ubiquitous today.

Were there a major risk of brain cancer from cellphone usage, it would have shown up in actual statistics. Hell, if the risk were as small as an extra one per million chance, we should still be able to find it (note that we're able to observe side effects that rare in the current COVID-19 vaccination drive). While the real world data is an uncontrolled study, the study size is so large that it has enormous statistical power in its own right.