I am not 100% sure what you want to achieve. But you write that you all have the same nationality, so maybe the normal "top finders" statistic does the trick? There is no need to indicate anything for the cache location, just the "nationality" of the finders. (In reality it's not the nationality but where PGC assumes you are living.) As a result you get a list of cachers with their finds broken down according to years. If you want one specific year only, you can filter additionally for logdate (from - to).
As an example the statistics for Belgium: https://project-gc.com/Statistics/Top?profile_country=Belgium&submit=Filter
. Note that all finds are included (whereever in the world) for cachers assumed to live in Belgium.