Thanks. I have seen serious estimates of 0.1% CFR for the 1957 and 1964 flu pandemics, but only notes saying that the seasonal flu CFR is <0.1%. Do you have a source for the 0.04% IFR?
But it seems plausible if the CFR is <0.1% as there are both asymptomatic cases of the flu and people don't always go to the doctor even if they have symptoms. It seems like caring about IFR was rare before this pandemic and the lockdown