September 18, 2026
Below is the full Convexa technical report for Friday, September 18, 2026, the most recent completed U.S. trading session.
1. Technical Diagnosis
At the headline index level, the session was moderately positive. The S&P 500 gained 0.17% to close at 7,650.50, the Nasdaq Composite advanced 0.40% to 26,522.55, and the Nasdaq-100 rose 0.67% to 29,644.17. The Russell 2000, however, declined 0.50% to 2,860.40.
The underlying market structure was materially weaker than the major indices suggested. On the New York Stock Exchange, declining issues outnumbered advancing issues by 1.78 to 1. On Nasdaq, 1,973 stocks advanced while 2,810 declined. At the same time, the S&P 500 recorded only 5 new 52-week highs against 30 new lows, while the Nasdaq Composite registered 45 new highs against 162 new lows.
The breadth profile of the S&P 500 was particularly notable. Only 19.08% of constituents were trading above their 20-day moving averages, 27.83% above their 50-day moving averages, and 49.50% above their 200-day moving averages. The index itself therefore remains near the upper end of its medium-term range while the majority of its constituents exhibit materially weaker technical structures.
The McClellan Oscillator deteriorated from −28 to −34. The S&P 500 14-day Relative Strength Index stood at 50.10, placing price momentum almost precisely in neutral territory while market breadth remained negative.
At the same time, the S&P 500 volatility index declined from 15.44 to 14.81, while the Nasdaq-100 volatility index fell from 19.96 to 19.29. From the perspective of index price action and implied volatility, the session appeared orderly. That apparent stability, however, contrasted sharply with the underlying condition of the broader market.
Technical diagnosis: headline indices remained stable, led primarily by the largest technology companies, while market breadth weakened again. The September 18 session was not a broad-based recovery; it was a concentrated advance in selected large-cap stocks against a backdrop of continued deterioration across the broader equity universe.
2. Core Technical Dashboard
| Indicator | Close | Change |
|---|---|---|
| S&P 500 | 7,650.50 | +0.17% |
| Nasdaq-100 | 29,644.17 | +0.67% |
| Nasdaq Composite | 26,522.55 | +0.40% |
| Russell 2000 | 2,860.40 | −0.50% |
| VIX | 14.81 | −4.08% |
| VXN | 19.29 | −3.36% |
| McClellan Oscillator | −34 | Previous: −28 |
| S&P 500 14-day Relative Strength Index | 50.10 | Near-neutral |
3. S&P 500 Moving Averages
S&P 500 close: 7,650.50.
10-day simple moving average — 7,632.29. The index is 0.24% above the average.
20-day simple moving average — 7,658.53. The index is 0.10% below the average.
50-day simple moving average — 7,617.09. The index is 0.44% above the average.
200-day simple moving average — 7,183.02. The index is 6.51% above the average.
The current configuration is:
200-day < 50-day < 10-day < price < 20-day.
This is a mixed technical structure. The S&P 500 remains above its 50-day moving average and has recovered its 10-day average, but has not yet regained the 20-day average. The 20-day average stands only approximately eight index points above the closing level.
4. Market Breadth
On the New York Stock Exchange, declining issues outnumbered advancing issues by 1.78 to 1.
On Nasdaq:
1,973 advancing issues;
2,810 declining issues.
The ratio of declining to advancing issues was approximately 1.42 to 1.
Within the S&P 500, a separate end-of-session dataset showed that only 150 of 496 constituents included in the sample finished higher. The equal-weighted S&P 500 declined by approximately 0.49%, while the capitalization-weighted index gained 0.17%. This represented one of the clearest divergences of the session.
Percentage of S&P 500 Constituents Above Moving Averages
| Horizon | September 18 | September 17 |
|---|---|---|
| Above 20-day average | 19.08% | 21.07% |
| Above 50-day average | 27.83% | 30.81% |
| Above 200-day average | 49.50% | 50.29% |
All three breadth measures deteriorated during the session.
The most significant divergence is clear: the S&P 500 itself remains above its 50-day moving average, while only 27.83% of its constituents remain above their respective 50-day averages.
McClellan Oscillator
September 17: −28
September 18: −34
The net number of advancing minus declining issues in the broader dataset was −1,149.
The oscillator remained below zero and deteriorated again following the improvement recorded on September 17.
5. New 52-Week Highs and Lows
S&P 500:
New highs — 5
New lows — 30
New lows exceeded new highs by a factor of six.
Nasdaq Composite:
New highs — 45
New lows — 162
New lows exceeded new highs by approximately 3.6 to 1.
This is particularly notable given that both the Nasdaq Composite and Nasdaq-100 finished higher. The headline indices advanced while the number of securities establishing new annual lows substantially exceeded the number establishing new annual highs.
6. Momentum
The S&P 500 14-day Relative Strength Index stood at 50.10.
This places the indicator almost exactly at the midpoint of its neutral range. The index is neither technically overbought nor oversold.
The neutral price-momentum reading nevertheless contrasts with weak market breadth: only approximately one-fifth of S&P 500 constituents remain above their 20-day moving averages.
7. Volume
Aggregate U.S. equity trading volume reached 25.29 billion shares, compared with a 20-session average of 16.19 billion shares.
Trading activity was therefore approximately 56% above the 20-day average.
This represents exceptionally high turnover relative to recent weeks. It cannot, however, be interpreted as confirmation of the headline index advance. Breadth on both the New York Stock Exchange and Nasdaq remained negative, while the equal-weighted S&P 500 declined.
Reliable final absolute figures for advancing and declining volume on the New York Stock Exchange were not confirmed by the available end-of-session public sources. No estimated or derived figures are therefore substituted.
8. Volatility
VIX
September 17: 15.44
September 18: 14.81
Change: −0.63 points, or −4.08%.
VXN
September 17: 19.96
September 18: 19.29
Change: −0.67 points, or −3.36%.
There was no direct price-volatility divergence. The S&P 500 and Nasdaq advanced while both VIX and VXN declined.
A more important second-order divergence was present, however: implied volatility declined while market breadth deteriorated materially. The options market therefore reflected relative stability in the major indices even as the broader equity market exhibited considerably weaker internal conditions.
9. Key S&P 500 Technical Levels
The nearest technical levels are:
7,658.53 — 20-day moving average and nearest overhead level;
7,632.29 — 10-day moving average;
7,617.09 — 50-day moving average;
7,183.02 — 200-day moving average.
The S&P 500 closed within a very narrow band between its 10-day and 20-day moving averages.
Nearest support zone: 7,617–7,632.
Nearest natural resistance level: approximately 7,659.
10. Key Divergences
Price versus breadth. The S&P 500 gained 0.17%, yet overall market breadth was negative and the percentage of constituents above their 20-day moving averages declined to 19.08%.
Capitalization-weighted versus equal-weighted S&P 500. The standard S&P 500 gained 0.17%, while the equal-weighted version declined approximately 0.49%.
Nasdaq-100 versus the broader Nasdaq market. The Nasdaq-100 advanced 0.67%, while Nasdaq recorded 2,810 declining stocks against only 1,973 advancing stocks.
Price versus new highs and lows. The S&P 500 advanced, yet new lows exceeded new highs by six to one. On Nasdaq, the ratio was approximately 3.6 to one.
S&P 500 versus Russell 2000. Large-cap stocks lifted the S&P 500 by 0.17%, while the Russell 2000 declined 0.50%.
Price versus McClellan Oscillator. The S&P 500 advanced while the McClellan Oscillator deteriorated from −28 to −34.
In aggregate, nearly all internal market indicators were weaker than the movement of the major capitalization-weighted indices suggested.
11. Technical Regime
Short-term: Bearish.
The S&P 500 is only marginally below its 20-day moving average and remains above its 10-day average, but breadth is exceptionally weak: only 19.08% of constituents are above their 20-day moving averages, the McClellan Oscillator remains negative, and new lows substantially exceed new highs.
Medium-term: Neutral.
The S&P 500 remains above its 50-day moving average, but only 27.83% of constituents are above their own 50-day averages. Price and internal market structure are therefore producing conflicting signals.
Long-term: Bullish, with material deterioration in breadth.
The index remains 6.51% above its 200-day moving average, which continues to rise. At the same time, the percentage of constituents above their own 200-day moving averages has declined to 49.50%, effectively moving below half of the market.
Main technical signal of the day: the advance in the S&P 500 and Nasdaq-100 was not confirmed by market breadth; internal market structure continued to deteriorate despite declining VIX and VXN.