| Series | First | Latest | Min | Max |
|---|---|---|---|---|
| Large caps (SPY) | 100.0 | 890.0 | 57.3 | 892.0 |
| Small caps (IWM) | 100.0 | 924.5 | 73.1 | 925.8 |
SPY and IWM adjusted close indexed to 100 at the shared startSPY (S&P 500 large caps) and IWM (Russell 2000 small caps), both daily, rebased to 100 at their shared start. Uses split- and dividend-adjusted close. When small caps lead they sit above large caps on the indexed scale; the gap is the small-cap premium (or discount) over the window.
As of 11 Aug 2026, the Large caps (SPY) line stands at 890.0 and the Small caps (IWM) line at 924.5 (both base = 100 at the shared start). The Large caps (SPY) line is up 22.7% over the past year and above its long-run median of 152.3.
When the IWM line runs above the SPY line, small caps are leading. Small-cap leadership is an early-cycle signal, marking recoveries, rising-rate regimes and domestic-growth rotations. When SPY leads, large caps are winning, typically during late-cycle periods, risk-off episodes or when mega-cap technology is doing the heavy lifting for the index. The current spread is roughly flat in the latest reading despite small caps holding a narrow lead.
SPY and IWM are the two most liquid ETFs covering large-cap and small-cap US equities, and both are total-return (split- and dividend-adjusted), so the comparison reflects the actual experience of an allocator sizing the size factor. Russell 2000 is the standard small-cap benchmark in the factor-investing literature, which makes the spread directly comparable to academic size-factor research.
The Russell 2000 is more cyclical, more domestic and more financially leveraged than the S&P 500, so the spread reflects sector and leverage effects on top of the pure size factor. IWM also carries higher turnover and front-running from index-rebalance flows. The window begins in May 2000, so it captures the dot-com unwind but misses earlier small-cap cycles. Treat the chart as context for the size factor, not investment advice.
On the rebased scale (100 at May 2000), IWM sits near 896 while SPY is near 851, so the cumulative spread is narrow: small caps lead by roughly 5 percentage points over the full 25-year window. Small caps led sharply through 2013-2014 during the post-crisis recovery, then underperformed badly through the 2015-2016 energy bust and the 2020-2024 mega-cap technology rally. The current reading reflects a modest small-cap recovery rather than a regime change.
Factor investors use the small-cap premium (small minus large) as one of the original Fama-French factors, and this spread is the live, investable version of that academic construct. Quants and factor allocators use the spread's direction and momentum to time tilts toward or away from small-cap exposure.
Small-cap leadership is a classic early-cycle signal: small companies with high operating leverage and domestic revenue bases tend to outperform when the economy is accelerating out of a recession. Large-cap leadership is a late-cycle or risk-off signal. Strategists use the spread, alongside the yield curve and PMIs, to label the business-cycle regime.
Because the S&P 500 is cap-weighted, sustained SPY outperformance can mean either broad large-cap strength or just a handful of mega-caps doing all the work. Allocators cross-reference this spread with the equal-weight-vs-cap-weight benchmark to distinguish broad large-cap leadership from mega-cap index concentration.
As of 11 Aug 2026, the Large caps (SPY) line stands at 890.0 and the Small caps (IWM) line at 924.5 (both base = 100 at the shared start). The Large caps (SPY) line is up 22.7% over the past year and above its long-run median of 152.3.
This benchmark is built on daily data. The page is refreshed when the source publishes new observations; the freshness block below the chart shows the exact data-through date and when PIER20 last fetched the file.
The chart is built from Large caps (SPY) and Small caps (IWM), sourced from Yahoo Finance.
Barely. Since May 2000 the IWM line has risen to roughly 896 while the SPY line sits near 851, so small caps lead by roughly 5 percentage points on the rebased scale. That narrow lead hides huge swings: small caps led sharply through 2013-2014 then underperformed badly during the 2020-2024 mega-cap rally, with the recent reading reflecting a modest recovery rather than regime change.
The summary callout measures how much the IWM line has outperformed (positive) or underperformed (negative) the SPY line over the selected window, expressed as a percentage. A positive reading means small caps have beaten large caps; a negative reading means large caps have won. The convention follows the catalog's 'small minus large' label.
Small-cap leadership historically clusters in early-cycle recoveries when domestic growth accelerates, in rising-rate regimes when smaller companies with floating-rate exposure can pass through costs, and during commodity booms when energy and materials small caps lead. The 2013-2014 post-crisis recovery was a clear example. The opposite regime, large-cap leadership, tends to dominate in late-cycle and risk-off periods.
This benchmark compares the small-cap universe (Russell 2000) with the large-cap universe (S&P 500), so it isolates the size factor across two different index universes. Equal-weight vs cap-weight compares two different weightings of the same S&P 500 constituents, so it isolates intra-index concentration. The two can diverge: large caps can beat small caps while equal-weight beats cap-weight, which happens when average large caps beat their own mega-caps.
One tested idea, through the evidence stack. No migration of any kind.