THE sharemarket had a good run this week, jumping above 4500 points on Wednesday and then closing yesterday at its highest for the year.
But the past couple of days were also bizarre, with questions raised about the integrity of the market after a series of unusual transactions on Thursday morning stoked fears of market manipulation.
For the week, the S&P/ASX 200 Index rose 84.6 points, or 1.8 per cent, to 4571.1.
Market watchers said the four-day rally was positive, given its composition: cyclical and resource stocks outperformed, while defensive stocks had a relatively bad week.
News that China's gross domestic product growth had slowed to 7.4 per cent in the September quarter its lowest since early 2009 failed to worry investors. It was seen as a sign that the world's second-biggest economy had started to stabilise, given its 2.2 per cent quarter-on-quarter growth had beaten expectations (of 2 per cent).
Investors also welcomed news from Spain that it had avoided having its credit rating slapped with a "junk status" sticker.
It helped Australia's miners shoot higher yesterday, with BHP Billiton jumping 3.3 per cent to $35, its biggest one-day rise in 10 months, while Rio Tinto rose 4.8 per cent to $59.15, its biggest one-day rise in 11 months.
But the week was also stained by questions about the integrity of trading on the ASX, after strange and ultra-fast transactions in the seconds before the opening bell stoked fears of market manipulation.
The trading world had already been on edge about the issue of high-speed algorithmic trading. So when on Thursday morning, in the seconds before the market opened, share prices in more than eight blue-chip stocks spiked dramatically, before falling just as quickly, alarm bells rang.
The Australian Securities and Investments Commission said it was looking into the issue, and the ASX said the same thing.
For the week, ASX rose 38? to $30.35 after the stock exchange proposed changes to its disclosure rules on market-sensitive information, following failed legal action against Fortescue Metals and a sham takeover bid for David Jones.
Lend Lease rose 52? to $8.76 after the developer said discrepancies in its construction company Abigroup's accounts were a one-off and would not affect results.
National Australian Bank rose 2? to $26.22 after it raised its provisions to deal with the economic downturn.
Santos climbed 42? to $11.99 after the oil and gas company maintained its full-year forecasts and achieved record quarterly sales, thanks to a steep increase in the gas price.
Telstra climbed 14? to $4.07 after defending the closure of Australian call centres, saying the loss of those jobs has been offset by the creation of others elsewhere in the organisation.