Musk’s net worth fell almost 4% as of midday Tuesday, dropping to almost exactly $100 billion below his all-time high of $464 billion.

Tesla's stock tumbled 8% on Tuesday, pushing its market value below $1 trillion for the first time since November after data showed the electric car maker's sales slumped in Europe in January.

Tesla stock has been weak lately as investors digest early sales data and try to determine whether a drop is due to random fluctuations—or something more serious. It’s still too early to tell, but the data aren’t great.