On September 18, 2026, Arbitrum's ARB token surged roughly 17% on the day and 26% over a trailing 24-hour window, reaching $0.2212. Starknet's STRK gained 18%, its highest price since June 19. Ethereum itself — the network both of these are built on top of — rose just 6.8% to $2,611.34 over the same stretch, per 24/7 Wall St's reporting. By September 21, ETH had climbed further to around $2,700, up 76% from its July 1 low of $1,550.
It's tempting to read that gap as ARB and STRK having better news than ETH that week. They did have real catalysts, covered below. But the size of the gap is mostly explained by something less exciting than news: market capitalization.
The math: same dollars, different denominators
Ethereum's market cap sits around $332 billion. Arbitrum's is roughly $1.4 billion — more than two hundred times smaller. Moving a $332 billion asset's price by a given percentage requires proportionally that much more capital than moving a $1.4 billion asset the same percentage. As the 24/7 Wall St piece put it: "the same buying pressure that lifted Ethereum by 7% also allowed ARB to surge 26%." Tens of millions of dollars in net buying is a rounding error against Ethereum's total value and a significant chunk of Arbitrum's daily liquidity. This is the same underlying mechanic covered in our guide to reading real trading signals — market cap and liquidity depth determine how far a given amount of capital can move a price, independent of how good or bad the underlying news actually is.
The catalysts were real, they just amplified an existing effect
Arbitrum did have a specific, datable news event behind it: Standard Chartered Research initiated coverage on September 16 with a $0.50 year-end 2026 price target and a $10 target for 2030, citing $6.19 million in DAO income generated by the Arbitrum Expansion Program in the first half of 2026 alone. That's the kind of institutional-coverage headline that tends to draw fresh buying into a token specifically. Starknet, meanwhile, released 127 million STRK tokens worth about $3.9 million on September 15 — a supply increase that could have pressured price — and the token rallied anyway just days later, a sign the unlock was small enough relative to trading volume to get absorbed without denting sentiment.
Layer on top of both of those the broader market backdrop: Bitcoin pushing above $80,000 and Treasury yields dropping below 5% gave the whole risk-asset complex a tailwind. Ethereum, notably, didn't have a comparable single catalyst that week beyond simply recovering back above the $2,600 level — which is itself part of the explanation for why it lagged its own Layer-2 tokens rather than leading them.
The pattern to actually remember
ARB has since pulled back to around $0.20, still trading roughly 91% below its 2023 peak of $2.39 — a reminder that a 26% day and a good year are two very different things. The durable lesson isn't about Arbitrum or Starknet specifically; it's that in any rally, smaller-cap tokens tied to a larger asset's ecosystem will reliably post larger percentage gains than the base asset itself, simply because they're smaller. That's neither a reason to chase them nor a reason to dismiss the move — it's a reason to check market cap before treating a percentage gain as a signal of relative strength.
Sources: 24/7 Wall St. Figures as reported at time of writing and subject to change.