TSP Market Summary: Week of September 20, 2025

By Roy Weisert, PhD, CFP

Key Takeaways

  • S&P 500 reached new record highs for third straight week, with small-cap stocks also surging
  • All three equity TSP funds (C, S, I) hit record highs with S fund leading performance rankings
  • Fed rate cut was positive but fewer future cuts expected than markets hoped for

The S&P 500 notched its third consecutive up week, closing at a new record high of 6,664. It was a before and after Fed decision week for the markets. On Monday we had some U.S. China trade and TikTok banter, but the big news was that Elon Musk purchased about $1 Billion (Yes, with a B) worth of TSLA shares, his largest buy in the open market ever and his first significant purchase since 2020. Investors saw this as a vote of confidence, and TSLAs shares surged about 7% as it turned positive on a Year To Date (YTD) basis. It was also a bullish day for Alphabet (GOOG) as it joined APPL, MSFT and NVDA in the $3 Trillion Mag 7 market cap club. As such, the S&P 500 rallied to a new record high and the NASDAQ 100 was up for its ninth day in a row. After that the markets took a breather awaiting the Fed rate decision on Wednesday afternoon. And at 1400 Fed Chair Powell announced a 0.25% cut in the Fed Rate and the markets immediately turned bullish. However, that was short-lived as during the press conference following the decision, Powell put a damper on investor hopes that the central bank would be on a lengthy rate-cutting path this year, as he called the latest cut risk management. In fact, policymakers were predicting two more reductions this year, but just one in 2026, while traders had priced in two to three more cuts next year. As such the S&P 500 sold off slightly, closing at a nice round 6,600. But the bulls awoke on Thursday morning with the S&P 500 gapping up at the open and continuing to a new record close. And it was not just Mega Cap stocks as the small cap-focused Russell 2000 surged 2.5%, ending the session at a record high for the first time since 2021. On Friday the bull kept charging as the S&P 500 closed at a new record high, while the Russell 2000 advanced for its seventh week in a row. From a technical perspective, on 30 August we mentioned that September has been the biggest losing month for the S&P 500 (-0.7%) since 1950. Well, it looks like the S&P 500 is on pace for an up month and making it five up months in a row, and we are looking forward to more of Letting the trend be our friend. For next week we get the final GDP number on Thursday, followed by the monthly Core inflation number on Friday. For TSP TIPS the analysis is similar to last week as all three equity funds (S/C/I) remain at maxed out Composite Scores, all hit new record highs, and the S fund remains at the top of the Performance Ranking leaderboard, followed by C and I. As such we again recommend no changes to our current investment mixes.