Nanex Research

Nanex ~ 20-Dec-2013 ~ LULD Snafu in ARIA

On December 20, 2013, the stock of Ariad Pharmaceuticals Inc (Symbol: ARIA, market cap: $1.9 Billion) rocketed higher, triggering 2 Limit Up Limit Down (LULD) circuit breakers which halted trading. Except that NYSE-MKT (AMEX) must not have gotten the message, because ARIA continued trading on that market (see charts 2-4 below).

1. ARIA LULD Bands (Gray Shading) and trading near those bands (red dots).
Note how the LULD bands shift significantly, which caused an almost immediate halt in the reverse direction!

2. ARIA Trades and NBBO.
Note how AMEX continues trading during one of the LULD halts.

3. ARIA Bids and Asks.
Amex continues trading and quoting during one of the LULD halts.

4. ARIA.
Zoom of Chart 1 showing the AMEX trades during a LULD halt.

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