U.S. Late-Day Stock Moves: SST, CHNG, TWTR, MKTX, CVNA

Advances:

• System1 (SST) +22.8%. SST reported strong fourth-quarter net income and revenue.
• Change Healthcare (CHNG) +7.5%. CHNG announced it would extend its merger agreement with UnitedHealth's (UNH) Optum.
• Twitter (TWTR) +2%. TWTR will appoint Elon Musk to its board.

Declines:

• MarketAxess (MKTX) -11%. Analysts are concerned about MKTX's weaker high-grade volumes and the negative impacts on its fee rates.
• Carvana (CVNA) -8.6%. CNVA shares were downgraded from "outperform" to "perform" at RBC.