at this stage it is virtually impossible to say what the average fatality rate overall would be across all age groups and cultures
as shown in a previous post it is very age dependent. The age demographics across continents and countries varies greatly. The developed countries have a greater aged % than the less developed countries (where more people live). Additionally there is varying health facilities and practices across countries. So, whilst under developed countries have a lower average age they also have lower health standards and support, consequently their fatality rate in the younger might be higher than the average for that age. Finally the virus is more virulent in cold weather so those countries close to the equator may be much better off
so to talk of an average fatality rate across the board or even an average by age is very difficult and potentially prone to great differences depending where in the world we are referring to.
fortunately however, the figures so far indicate a relatively low fatality rate (cf other deadly pandemics)