Tesla and Netflix did nearly 80% of Consumer Discretionary's damage today

Consumer Discretionary was the worst-performing of the S&P 500's eleven sectors on September 4, falling 1.39% market-cap weighted while the index itself closed down 0.34%. Almost none of that decline was broad-based: $TSLA and $NFLX together erased $106.4 billion of market cap, out of the sector's $134.8 billion total loss for the day — about 79 cents of every dollar the sector lost.

Where the sector's move came from

Pull $TSLA and $NFLX out of Consumer Discretionary and the other 53 members of the sector were down just 0.37% together — in line with the index, not worse than it.

Breadth tells the same story

Of the sector's 55 members, 32 fell and 23 rose, and the median stock moved just -0.14% — nowhere near the sector's -1.39% cap-weighted average. That gap between the median move and the cap-weighted move is itself the signature of a decline concentrated in a couple of large names rather than one hitting the whole group.

Tesla's worst day in at least six weeks

$TSLA closed at $354.08, down 5.92% from Thursday's $376.37 close — its largest single-day decline in at least the last 29 trading sessions on our data, a stretch going back to late July. The drop wiped out roughly $88.0 billion of market cap in one session.

The move came the same day Tesla's Cybercab robotaxi service launched in Austin. MarketWatch described the reception as landing "with a thud," and the National Highway Traffic Safety Administration opened a probe into the rollout the same day, a vehicle with no steering wheel or brake pedal being deployed on public streets, according to the Wall Street Journal and ABC News.

The stock had run up ahead of the drop: on September 3 it closed 5.0% above its own 50-day moving average, with an RSI(14) of 60.5. The decline pulled it to 1.1% below that average and an RSI of 50.9 by the close on September 4, on our data.

Netflix added to the drag

$NFLX closed down 5.35%, a loss of roughly $18.4 billion in market cap. TipRanks and Yahoo Finance both tied the move to Netflix raising its U.K. subscription prices, with outlets noting the U.K. accounts for a meaningful share of the company's EMEA revenue.

Netflix had run up further than Tesla had: it closed September 3 at 9.8% above its 50-day average. September 4's drop cut that premium to 3.7%, still positive but the smallest gap of the week.

The scale of it

The S&P 500 lost about $278.3 billion in total market cap on the day. Tesla and Netflix's combined $106.4 billion loss was equivalent to more than a third of that — from two names, in a 500-stock index, on a day with no sector-wide news event tying them together.