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 electronic trading platform service MarketAxess (Nasdaq: MKTX) dipped as much as 12% in early trading today after receiving an analyst downgrade before the opening bell.

So what: Brokerage firm Stifel Nicolaus is the culprit, downgrading MarketAxess to "hold" from "buy" early this morning. The brokerage cited weak August statistics, as well as valuation concerns, as the impetus for the downgrade. Just yesterday, MarketAxess reported $44.4 billion in monthly trading volume, which is down from the $47.1 billion in reported in August 2011.

Now what: First off, it's rarely worth changing your investment thesis because of a one-day bump or drop caused by an analyst call, so let's more or less ignore it completely. What is worth paying attention to is the lull in trading volumes across the board. Daily average revenue trades are a key metric for measuring brokerage firms' ability to attract new trading volume, and in July TD AMERITRADE (Nasdaq: AMTD) reported a 9% decline in DARTs, and Charles Schwab (NYSE: SCHW) reported a 2% decline. Although TD AMERITRADE and Schwab cater to a different customer than MarketAxess, there's notable weakness across the sector, and until that improves, I wouldn't expect there are enough catalysts to push any of these financial service companies higher.

Craving more input? Start by adding MarketAxess to your free and personalized Watchlist so you can keep up on the latest news with the company.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.