The feed is the price STEEM/USD... at the time of writing, the top19 sampling will give a median of $2.13 per STEEM, which is slightly higher than markets prices on poloniex or Bittrex... To help restore SBD to parity, the witness should adjust this price slight downwards...
maybe a 5% for the first try, then watch the market response before taking futher adjustment....
RE: Do Your Part to Restore the SteemDollar Parity.