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Well all the data should be available, it's just a matter of someone making a site or something that breaks it down. For starters this API call shows the balances of all the DEC inflation and burning related accounts, so if you just look at the difference in the balances over a time period you can see how much DEC was created and burned over that period:

https://api.splinterlands.io/players/balances?token_type=DEC&players=$INFLATION,$BURNED_CARDS,$SHOP,$DEC_REWARDS

$INFLATION is the DEC created for ranked battle rewards, $BURNED_CARDS should be self-explanatory, $SHOP is DEC burned for shop purchases, and $DEC_REWARDS is DEC created for quest and season rewards.