SYDNEY -- A strong showing from the U.S. stock market indexes and a positive lead from the ASX SPI weren't enough for our market to close the week on a positive note, with the S&P/ASX 200 (INDEX: ^AXJO) closing down 0.3% to 4,362.1 points and the All Ordinaries (INDEX: ^AORD) off by the same margin to close at 4,433.4.

A good lead from Wall Street
Our market was unable to capitalize on another night of gains on Wall Street, where the Dow Jones had put on 0.9%, while the S&P 500 and the Nasdaq had both risen 0.7% -- even before another blowout quarter from Amazon.com (Nasdaq: AMZN) that pushed the company's shares up 8% in after-hours trading.

The circuit breaker may have been some sobering news from Europe, where Spain's credit rating was downgraded after the U.S. market had finished trading (as had our own ASX SPI futures index). Standard & Poor's took its view of Spain's creditworthiness down two notches to "BBB+" in yet another sign (if one was required) that Europe is far from being back on its economic feet.

Structural changes play out
As if to underline the continued divide between the corporate "haves" and "have-nots" of the current economy, the profit numbers released today neatly illustrated the sectors that are going from strength to strength and those that are still in the economic emergency room.

Amazon's profit numbers (and recent announcement that it is going to open a business-to-business portal called AmazonSupply) only served to underline the degree to which consumer (and maybe business) spending is migrating online. And today's profit numbers from JB Hi-Fi (ASX: JBH) only served to demonstrate the businesses that are ceding ground to the relentless advance of Amazon and its ilk.

Results have an impact...
Investors went cold on some in the consumer discretionary sector in light of JB's results, with competitor Harvey Norman losing 2.4%, Myer dropping 2.9%, and The Reject Shop falling by 0.9%. It wasn't all doom and gloom, though, with David Jones showing gains of 0.8% and Super Retail up 2.1%.

In other profit news, Macquarie Group shareholders seemed to breathe a collective sigh of relief that today's profit results weren't even worse than the 24% drop, sending shares up 3%.

Also in the good news department was Resmed (NYSE: RMD), which delivered gains of 5.8% on another strong quarter of sales and profit growth both in double digits.

...as does a possible takeover
Speaking of good news, there were some impressive gains for shareholders of struggling PMP after management revealed that a "highly conditional, non-binding, indicative" bid had been received by the company. I'm not sure if it's possible to be less committal, but shareholders (and speculators) seemed to like the news, sending shares up a full 148% in the course of one day's trade.

It's a cautionary tale for anyone who lets sell orders just sit in a broker's system. Pity a poor investor who'd set a sell order at 5% or 10% above the then-current price; he or she would have missed out on the next 130% of gains.

Sector moves
In sector moves, only two sections of our markets managed gains on the last trading day of the week, with the utilities sector up 0.7% and information technology putting on a 0.6% gain.

Of the sectors going backwards today, the materials and health-care sectors led the way, both down 0.6%, followed by the energy sector, down 0.5%.

Individual stocks on the ASX 200 showed quite a broad range of returns. Fifteen gained 2% or more, and 18 fell by a similar quantum, with 16 percentage points between the highest gainers and biggest losers.

The biggest winners and losers
Among the former group, the gains were led by Resmed, but another four companies managed gains in excess of 3.5%, with Coalspur Mines up 4.5% and Intrepid Mines gaining a similar amount, while St Barbara, up 3.7%, and Platinum Asset Management, up 3.6%, rounded out the top five.

Leading the downward charge on the ASX 200 list today was Imdex, down 10.1%, with investors obviously not responding well to the company's third-quarter announcement. There were a few other ASX 200 companies also nursing heavy losses today, with Bathurst Resources down 7%, the aforementioned JB Hi-Fi losing 6.3%, FKP Property off 4.9%, Senex Energy falling 3.5%, and Alacer Gold closing 3.4% lower than yesterday's closing price.

Foolish takeaway
We're used to resource businesses being volatile, but it's hard to escape the possibility we're seeing something of a structural change play out, with medical devices growing (as we age, spend more on health care, and fall victim to more "lifestyle" diseases) and traditional retailers continuing to be squeezed by changing technology and shopping preferences.

As always, we hesitate to put too much weight on a day's share-price movements, but in this case it's the underlying business results that are telling the story.

The ASX is already on the move in 2012, and Goldman Sachs experts recently said they reckon the S&P/ASX 200 could top 5,000 next year. "Read This Before The Coming Market Rally" is a must-read for investors who don't want to miss out on the party. Click here now to request your free copy, before it's too late.

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Scott Phillips is an investment analyst with The Motley Fool. Scott owns shares in Telstra. You can follow him on Twitter @TMFGilla. Take Stock is The Motley Fool Australia's free investing newsletter. Packed with stock ideas and investing advice, it is essential reading for anyone looking to build and grow their wealth in the years ahead. Click here now to request your free subscription, while it's still available. This article contains general investment advice only (under AFSL 400691).