iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
In 2026, the answer depends on the time window: stocks beyond the mega-cap leaders participated broadly in the first half, but September gains narrowed sharply. Higher Treasury yields added pressure to rate-sensitive and cyclical shares, according to VanEck, though the available evidence does not show that rates alone caused the weakness.
Why are mega-cap stocks rising while small-cap stocks lag?
They did not lag throughout 2026. In the first six months, the S&P 500 rose 10%, while the S&P MidCap 400 gained 17% and the S&P SmallCap 600 gained 24%, according to S&P Dow Jones Indices. The index provider also reported that more than 60% of stocks beat the S&P 500 in June and July in its August 11 analysis (S&P Dow Jones Indices).
September looked different. VanEck reported that the cap-weighted S&P 500 fell 0.35%, while the S&P 500 Equal Weight Index dropped 4.81%. Technology was the only sector to end the month higher (VanEck). The gap indicates that the largest companies had a much stronger effect on the headline index than the average constituent did that month.
What the index comparison tells you
A cap-weighted index gives more influence to companies with larger market values. When a small number of mega-cap stocks hold up better than the rest of the market, they can soften a benchmark’s decline or lift it even while many constituents fall. An equal-weight index gives each constituent the same weight, making it a useful contrast—but it is not a measure of small-cap performance. Mid- and small-cap benchmarks answer that separate question.
#1 Best Overall
| Measure | Period | Reported result | What it helps show |
|---|---|---|---|
| S&P 500 | First six months of 2026 | Up 10% (S&P Dow Jones Indices) | Cap-weighted large-company performance |
| S&P MidCap 400 | First six months of 2026 | Up 17% (S&P Dow Jones Indices) | Mid-cap performance |
| S&P SmallCap 600 | First six months of 2026 | Up 24% (S&P Dow Jones Indices) | Small-cap performance |
| S&P 500 | September 2026 | Down 0.35% (VanEck) | Cap-weighted large-company performance |
| S&P 500 Equal Weight Index | September 2026 | Down 4.81% (VanEck) | How the broad set of S&P 500 constituents fared with equal weights |
These figures cover different time periods, so they should not be read as a continuous comparison. Together they show a change in relative breadth: mid- and small-cap stocks outperformed in the first half, while September’s equal-weight result was much weaker than the cap-weighted S&P 500.
How higher yields can affect stocks—and what they do not prove
Higher borrowing costs can weigh on companies that depend on financing, and higher yields can make future earnings less valuable in present-value calculations. Those pressures can matter particularly to rate-sensitive businesses and cyclical areas of the market. VanEck said higher rates and Treasury yields added pressure to those groups in September (VanEck).
Rank #2
- Comes with secure packaging
- Easy to read text
- It can be a gift option
That is an explanation of pressure, not proof that interest rates alone caused any stock’s decline. Sector composition, company-specific news and earnings also affect relative performance. In its July report, the Federal Reserve cited robust corporate earnings and enthusiasm about artificial intelligence as factors supporting the S&P 500 and information-technology gains at that time (Federal Reserve). Those observations concern an earlier reporting period, not current October returns.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsWhat the October 5 snapshot can—and cannot—say
The latest direct market-close evidence here is an Associated Press report dated October 5, 2026. It put the 10-year U.S. Treasury yield at 5.31% amid oil-market concerns and described the S&P 500 as near its summer record (Associated Press). That snapshot shows a strong headline index coexisting with an elevated yield; it does not establish the market’s breadth on October 7 or show that every stock was advancing.
For a current read, check the date range and compare cap-weighted and equal-weight index returns alongside mid- and small-cap benchmarks. Also look at sector performance and Treasury yields. A headline index level by itself cannot tell you whether gains are broad or concentrated.
Quick Recap
Best Value
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
