Trade Desk (TTD.US) soared over 9% on Tuesday, reaching a five-month peak at $82.43. This rally follows S&P Dow Jones Indices' announcement that the digital advertising platform will join the S&P 500 index before Friday's market open. Trade Desk will replace engineering software firm Ansys, which is being acquired by Synopsys in a transaction expected to close Thursday.
The inclusion came as a surprise to market participants, given Trade Desk's $37 billion market capitalization falls significantly below the typical threshold for S&P 500 constituents. This unexpected index reshuffle provided immediate trading impetus, driving the stock to its highest level since late August.