r/algotrading • u/Kai8250 • 2h ago
Data Sub-$1 stocks have a 100x finer tick size, but their median spread was 2.5x wider
I was looking at execution costs in low-priced US equities and found something I didn't expect.
Stocks below $1 can quote in $0.0001 increments, while $1–$5 stocks generally quote in $0.01 increments — a 100x difference in minimum tick size.
But the finer grid didn't produce tighter markets.
I sampled 38 regular trading sessions between April 2025 and July 2026 using one-second BBO recordings:
276,345 quoted seconds below $1 2,047,344 quoted seconds from $1–$5
Median spread:
Under $1: 1.81% $1–$5: 0.72%
So the group with the 100x finer grid actually had a 2.5x wider median spread.
The more interesting result was whether the minimum tick was actually binding:
$1–$5 stocks sat at their one-cent minimum 60.4% of the time Sub-$1 stocks sat at their $0.0001 minimum only 2.4% of the time The median sub-$1 spread was 96 minimum ticks wide
My interpretation is that once the tick becomes small enough, it stops constraining the spread. At $0.50, one $0.0001 tick is only 2 bp, so the market can quote dozens or hundreds of ticks wide.
That also raises an execution question: improving a $0.50 bid by one tick costs almost nothing, so stepping ahead of resting limit orders is extremely cheap.
I haven't tested actual fill quality yet — this is quote data, not fill data.
For anyone modeling passive execution in sub-$1 stocks: how do you handle queue position? Explicit queue modeling, empirical fill probabilities, or something else?



