The takeaway
SEI Investments Company shows a slight seasonal lean over 10 years of data — strongest in December (+1.1%) and softest in September (−1.6%).
Right now
In July, the stock has risen 50% of years, averaging +0.2%, roughly 2.0 pts behind the S&P 500.
The full picture
SEI Investments Company's most dependable month has been December, higher in 8 of 10 years; September has been its least reliable, up just 30% of the time.
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Month by month
The stock's clearest edge over the S&P 500 lands in November (+2.7 pts); it has trailed the market most in February (−2.1 pts).
“vs S&P” is SEI Investments Company’s average for a month minus the S&P 500’s average for that same month — isolating SEI Investments Company’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, December has closed higher 80% of the time versus 80% across the last 10 years — the pattern is holding.
Figures are the typical (median) December return and how often it rose — the last 5 years versus the last 10(the heatmap’s default window). This verdict stays anchored to that 10-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
This is a stock you can almost set a calendar by, and December is the anchor — it has closed higher in 8 of 10 Decembers, the steadiest beat on its year.
The strength looks broad-based rather than freakish: its average (+1.1%) and median (+3.2%) sit close together, so no single blow-out year is flattering the figure. Set against the S&P 500, mind, December is close to a wash — the gain mirrors the market more than it beats it. Few peers keep such company in December — the typical stock clears it just 58% of the time.
It doesn't stand entirely alone — April, May, and August have leaned firm as well, if less emphatically. At the other end of the calendar, September has been the soft spot — the weakest of 3 months that average a loss (−1.6%), and the edge isn't year-round — the stock has trailed the S&P 500 in February, July, and January. Its roughest month on record was a −23.0% January in 2016 — a reminder of how hard even a seasonal name can fall.
Reassuringly, the tendency has held its shape: the recent five years still track the years behind them.
For a stock this dependable in December, the sharper question is the rest of the year — outside its strong stretch, the calendar gives far less to lean on.
Short answers on the stock's best month (December), its worst (September), and whether it really trades seasonally.
Only mildly. The stock's months are fairly even — December is the firmest (+1.1%) and September the softest (−1.6%), a narrow spread that points to weak seasonality rather than a strong calendar effect.
December has been the strongest, averaging +1.1% and closing higher in 8 of 10 years since 2016.
It's the weakest, averaging −1.6% — historically a soft spot, though it still varies from year to year.
Explore
These names have the strongest July track records on record — a starting point for comparison.
Before you trade