The takeaway
Delcath Systems Inc shows a pronounced seasonal pattern over 10 years of data — strongest in May (+7.8%) and softest in October (−17.0%).
Right now
In July, the stock has fallen 33% of years, averaging −12.6%, roughly 14.8 pts behind the S&P 500.
The full picture
Delcath Systems Inc's most dependable month has been May, higher in 5 of 8 years; October has been its least reliable, up just 20% of the time.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
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| 2018 | — | — | ||||||||||
| 2017 | — | — | ||||||||||
| 2016 | — |
Month by month
The stock's clearest edge over the S&P 500 lands in August (+10.1 pts); it has trailed the market most in October (−18.0 pts).
“vs S&P” is Delcath Systems Inc’s average for a month minus the S&P 500’s average for that same month — isolating Delcath Systems Inc’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, May has closed higher 60% of the time versus 63% across the last 10 years — the pattern is strengthening.
Figures are the typical (median) May 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
May looks the standout, up in 5 of 8 Mays — yet the appeal is lumpy, leaning on the occasional blow-out year rather than dependable strength.
The headline flatters a touch — its +7.8% average sits well above the +1.4% a typical year delivers, the work of a few big Mays. That reliability comes with real swings, mind — even May ranges by 21.6% from year to year, so any single year can land far from the average. Crucially, the gain is the stock's own rather than a rising tide's: May has cleared the S&P 500 by +7.1 points above the index.
Only August comes anywhere near it for reliability. The weaker half of the year is plainer: October has been the soft spot — the weakest of 8 months that average a loss (−17.0%), and the edge isn't year-round — the stock has trailed the S&P 500 in October, July, and September. Its roughest month on record was a −73.3% October in 2018 — a reminder of how hard even a seasonal name can fall.
If anything it has sharpened recently — the last five Mays run ahead of the earlier years.
Hold it loosely, then: the May tendency is genuine but lumpy, more about the occasional outsized year than a gain to bank on. With returns that swing hard year to year, the signal is best held loosely.
Short answers on the stock's best month (May), its worst (October), and whether it really trades seasonally.
Yes, to a pronounced degree. Since 2016 its best month (May, +7.8%) has run well ahead of its worst (October, −17.0%) — the heatmap above shows how steady that gap has been year to year.
May has been the strongest, averaging +7.8% and closing higher in 5 of 8 years since 2016.
It's the weakest, averaging −17.0% — 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