Tesla is trading more like SpaceX than a car company

Tesla still sells cars. Its stock has stopped trading like it.

Over the past 20 sessions, the daily moves of Tesla ( TSLA ) have had a correlation of 0.64 with SpaceX ( SPCX ), according to Yahoo Finance calculations. Correlation measures how consistently two stocks move in the same direction, where 1 means they always move in lockstep. In SpaceX's first 20 sessions after its June IPO, the reading was just 0.15.

The two stocks finished in the same direction on 15 of the last 20 days.

Tesla's correlation with GM ( GM ) over the same stretch is -0.10, and with Ford ( F ) it's -0.14. Both readings were positive throughout the summer, mostly between 0.3 and 0.4.

Since Sept. 14, when Elon Musk first hinted at a combination between the two companies, Tesla has gained about 4% through Tuesday, while GM and Ford have each dropped more than 11%.

Tesla still tracks the Nasdaq-100 ( QQQ ) a little more closely than it tracks SpaceX, with a correlation of 0.71. Both are big, volatile, tech-heavy stocks, so part of their tight link comes from riding the same market.

But strip out the Nasdaq-100's moves, and the two still move together more than they used to. The leftover correlation between Tesla and SpaceX is 0.32, up from readings as low as -0.52 in July and August, by Yahoo Finance calculations. That leftover bears the fingerprints of the merger trade.

The merger talk has gotten louder. On Tuesday, Musk said both companies have formed special committees to explore the idea .

Cantor Fitzgerald analyst Andres Sheppard told Yahoo Finance on Tuesday that a merger will "likely happen and possibly under 12 months."

Bespoke Investment Group has spotted the same pattern , noting the two have been "increasingly trading in the same direction."

In any deal, Tesla would be the smaller partner. SpaceX is worth about $2.25 trillion, compared with about $1.52 trillion for Tesla.

A 20-session correlation can unwind as quickly as it was built, though. It shows what traders are betting on, not that a deal is coming.

The first test arrives after Wednesday's close, when Tesla reports third quarter results. Options are pricing a 5.4% move, according to Bloomberg data. Tesla's actual median move the day after earnings since 2023 has been closer to 10% in either direction, by Yahoo Finance calculations.

Watch whether Tesla trades on its own numbers or on SpaceX's. If the two split apart after the report, the merger trade might just be losing its grip. If they move together again, the market is already treating them as one company.