Equal-weight S&P 500 fund fell 4.8% over a month while SPY rose 0.4%

Thursday’s weak typical stock was not a small-cap story. The Russell 2000 fund AIWM fell 0.08%, in line with the cap-weighted S&P 500 fund ASPY. Small-caps have been weak on their own: AIWM is down 5.6% over the past month. Thursday, it was the S&P 500’s own typical stock, equally weighted, that slipped. The equal-weight S&P 500 fund BRSP is down 4.8% over that month against ASPY’s 0.4% gain, a 5.2-percentage-point hole. Thursday was more of the same split.

The S&P 500 closed at 7,703.83, down 0.03%, a session the weekly chart will swallow. BRSP fell 0.50%. ASPY fell 0.08%. BRSP lagged ASPY by 0.41 percentage points on the session, the month in miniature. Wednesday the index and the stock-by-stock count fell together. Thursday only the count kept falling. Of 5,841 U.S. common stocks listed on the NYSE, Nasdaq and NYSE American, 3,272 declined and 2,308 advanced.

Meta held ASPY near unchanged

Eleven of the twenty largest U.S. stocks finished higher. That is not the same as the mega-caps carrying the market. Nine of those twenty fell, including Nvidia, Microsoft and Apple. The work of holding ASPY near unchanged came from a shorter list.

Meta Platforms rose 4.5% and contributed 0.11 percentage points to ASPY, the largest single contribution in the fund. Nvidia, still 8.2% of ASPY, subtracted 0.03 percentage points. Alphabet, Eli Lilly and Advanced Micro Devices helped on the margin; Broadcom, Microsoft and Apple took some of that back.

Lilly had a dated reason. The Food and Drug Administration approved Onswik, the drugmaker’s once-weekly basal insulin, for adults with type 2 diabetes. Meta was still on the Muse run that already lifted it 11% on Monday. Oracle fell 3.5% after citing force majeure on a New Mexico data-center project. Intel rose 3.9%. Walmart fell 2.7%. The Nasdaq-100 fund AQQQ finished 0.01% lower.

Same 500 companies, different weights

BRSP owns the same 500 companies ASPY does. It does not own them the same way. Technology is 17% of BRSP and 39% of ASPY.

The ten largest names are 39% of ASPY; BRSP resets toward a fifth of a percent per stock. BRSP also carries more utilities and real estate, 5.6% and 5.5% against ASPY’s 2.0% and 1.8%. The utilities sector fund AXLU is down 8.4% over the past month; the real estate sector fund AXLRE is down 7.4%.

Part of the 5.2-percentage-point gap is that mix, not a pure headcount of who rose. One AI-agent rally and one insulin approval can hold the cap-weighted fund still. They cannot hold the equal-weight fund.

ASPY’s 0.4% month is a description of that 39% technology weight and those ten names. BRSP’s 4.8% decline is a description of the other 490. They are the same 500 companies. They have not been the same holding. ASPY can keep showing a different month than the typical stock for as long as those weights hold. Thursday they held.