What happened
Shares of Tesla (NASDAQ: TSLA) were hit hard on Wednesday. The stock fell 4.8% by the time the market closed.
The stock is likely down primarily because of a decline in the overall market that weighed particularly heavily on growth stocks like Tesla. However, shares may also be down because of a note from Morgan Stanley analyst Adam Jonas about Ford's new electric Mustang Mach-E taking market share from Tesla in February.

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So what
Jonas estimates that Tesla's market share of the EV market in the U.S. dropped from 81% in February of 2020 to 69% in February of 2021, largely due to market share gains from the new Mustang Mach-E.
Still, this doesn't mean Tesla's electric vehicle sales are faring poorly; the overall EV market grew 40% year over year during the period, Jonas estimates.