NYSE’s halt will go down as the biggest interruption to U.S. stock trading in two years. The last of comparable scope occurred in August 2013, when the Nasdaq Stock Market halted trading not only on its own platform, but anywhere stocks that it listed changed hands.

At the same time, the malfunction highlighted the resilience of a market structure where no single venue handles more than 16 percent of overall market volume. Other exchanges such as Nasdaq and Bats kept operating as normal throughout the suspension.

Eoin Treacy's view

The fact the NYSE only accounts for 20% of trading volume has insured this event did not cause a market rout. However it is just not good for confidence. Investors need to know they can transact in any way they wish and having a major exchange offline for hours during a time of market stress is one more reason to de-risk.

The S&P 500 posted an upside key day reversal yesterday but dropped today to countermand that upward dynamic. The Index is now back in negative territory for the year and a bounce similar to yesterday’s will be required to question current scope for a further test of underlying trading. 

The Dow Transports Index continues to extend its downtrend and is now in the region of the October lows near 8000. A break in the short-term progression of lower rally highs will be required to suggest a reversionary rally is underway and to question downward momentum. 

The Russell 2000 has returned to test the region of the 200-day MA and will need to hold the 1200 area if medium-term potential for higher to lateral ranging is to be given the benefit of the doubt. 

The Nasdaq-100 dropped down out of its three-month range today and a clear upward dynamic will be required to signal a return to demand dominance. 

The 20 area on the VIX Index has offered resistance on a number of occasions over the last three years. A sustained move above it would suggest more than temporary easing within the overall uptrend is underway for the above indices. 

The iShares Nasdaq Biotechnology ETF failed to sustain the move to new highs in late June and is now in a process of mean reversion.