That could still be true. I imagine there are a huge number of variables that influence mortality rates, to the point where finding correlations is difficult.

That could still be true. I imagine there are a huge number of variables that influence mortality rates, to the point where finding correlations is difficult. If I understand correctly, even the effect of weather/heat on various strains of viruses is extremely difficult to predict because of how many other factors play a role (air-conditioning, for example).