As a little bit of extra information, it's now been exactly 2 days since this comment and the Circulating Supply has increased to 463,419,656 (+148,862) which equates to 521,017 per week. Rounding down to 521,000.

12,000 / 521,000 = approximately 2.3%

So currently, approximately 2.3% of newly minted crypto is burned.

Unfortunately, I don't think it's quite that simple. Remember that:

1. When the price of STEEM is above the SBD print threshold, rising prices reduce the virtual supply and falling prices increase it - regardless of what's happening with token burning.
2. When the SBD market cap is between 9% and 10% of the STEEM market cap, the SBD print percentage changes. This means that the current_supply for STEEM and SBD don't grow in direct proportion to the blockchain inflation rate. The blockchain has been in this state for some time now.

By comparing before and after March 1, you can see here (source), how the changing price of STEEM influences the daily changes in the current supply (green line). I don't think it's possible to pick token burning out from all the other noise.

I agree with this point, but it doesn't bother me:

I'm inclined to still conclude that it's probably not achieving much at its current scale.

To me, burning shouldn't be about manipulating the price. It should be about (i.) providing a tool for authors to grow their audience; and (ii) giving the tokens a purpose. Any change to token price is just a side-effect.

I don't know the numbers as a percent of supply, but - coincidentally - I just posted the nominal burn amounts, here, as-of today.

According to that chart (which is based on the beneficiary reward operations from the blockchain), we see 3702 SP + 1730 STEEM + 549 SBD burned in the last week. If we say each SBD is 3.8 STEEM (~ $1 / $0.26 ), then that's ~7518 STEEM. There are about 90k in rewards each day, so 630K for the week. That works out to about 1.2% of newly minted STEEM (or STEEM equivalent) getting burned. My guess is that most of the difference between 1.2% and 2.3% could probably be attributed to STEEM price movements (also, witnesses are missing about 70 blocks per day, so that's another ~1500 STEEM per week that's being pseudo-burned (https://steemdb.io/witness/misses)).