ETrade will not tell you the percentages but I just played with system and my margin buying power dropped $20,000 with a 1,000 share order (limit $12 to ensure no stupid execution). The buying power is calced based on 30% margin so a drop of $20K (vs. $12K implied in buying power) means their margin is 167% of standard, or 50%, which foots with other changes in account health. There may be something quirky going on given low buying power in the account (cash is off elsewhere doing other things) but this should be close.
As I had mentioned earlier, Schwab went from 30% to 50% margin requirement in my account after my RPRX had gone up 100%. I wonder if they put limitations on stocks that not only move down sharply, but up sharply, as was the case with RPRX.
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