Should Tesla Chief Executive Elon Musk be sending a thank-you letter to the Federal Reserve? Put another way: Is it more than coincidence that Tesla’s stock—and the rest of the market—has soared since the Fed starting buying Treasurys again in October?

The answer is that the Fed probably isn’t the cause of the stunning rally in Tesla or stocks more broadly, at least in the usual way of thinking about causes. On the other hand, if the Fed hadn’t acted, the market would almost certainly be lower, possibly disastrously so.

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