Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of technical and management support services specialist AECOM Technology (NYSE:ACM) plunged 12% today, after its quarterly results and guidance missed Wall Street expectations.

So what: The stock has rallied in recent months on a string of new contract wins, but a small third-quarter revenue miss -- $2.08 billion versus the consensus of $2.2 billion -- coupled with downside guidance for the full year, is forcing Mr. Market to dial back his expectations. While AECOM's EBITDA margins came in at a record 12%, persistent weakness in the global economy continues to weigh on demand.

Now what: Management sees full-year 2013 EPS of $2.40 to $2.50 on flat year-over-year revenue of $8.2 billion, below the consensus of $2.59 and $8.6 billion. "Our results clearly demonstrate the progress that we've made to drive a performance culture committed to improved growth, profitability and liquidity," Chairman and CEO John Dionisio reassured investors. With the stock now off 20% from its 52-week highs and trading at a forward P/E of about eight, now might even be an opportune time to buy into that optimism.

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