THE Australian share market has shed close to $50 billion in value after a “perfect storm” on Wall Street caused heavy stock losses across every other sector.

It’s been reported it was the worst close for the ASX since the 2016 Brexit referendum in the UK, with $49.6 billion wiped from the boards.

After plunging at the opening, the benchmark S&P/ASX200 index slid down 166 points, or 2.74 per cent, to 5883.8 points at 4.15pm Sydney time today, while the broader All Ordinaries was down 170.4 points, or 2.76 per cent, at 5993.4.

The SPI200 futures index was down 165 points, or 2.74 per cent, at 5858 while the Aussie dollar battled against the tide to be worth 70.74 US cents, up from 70.44 at the close on Wednesday.

Afterpay was the worst performer on the Australian share market. Tech-related shares suffered the biggest decline, the sector shedding more than 4.5 per cent off the back of a poor US session.

Energy and healthcare also took a beating, while the heavyweight financial and materials sectors were in the doldrums.

Telco giant Telstra was down 1.4 per cent after it apologised to shareholders for a lack of clarity about how it calculates executive bonuses, acknowledging that some investors still feel they are too high despite a 30 per cent cut.

Shares in CSL, which held up the market on Wednesday, had fallen about 1.5 per cent, while Cochlear Limited had lost more than two per cent.

Only gold miners and Fortescue Metals Group were offering any real relief as investors sought safe haven, recovering from yesterday’s flat trade to push Evolution up more than 4 per cent and St Barbara up more than 4.8 per cent at noon.

Fortescue Metals Group has launched a share buyback program of up to $500 million ($US355 million), joining bigger rival Rio Tinto in handing back cash to shareholders.

Shares in FMG were up 1.36 per cent to $3.72, while BHP are down 2.62 per cent at $33.81, a fall only marginally worse than fellow mining giant Rio Tinto’s 2.43 per cent to $77.25.

The Aussie dollar was keeping its head above water, buying 70.65 US cents from 70.13 on Wednesday.

The big four banks were between 1.22 and 1.9 per cent lower, with ANZ leading the quartet lower.

Commonwealth Bank chief executive Matt Comyn appeared before the House of Representatives economics committee while the market was opening with Westpac chief Brian Hartzer also to front the hearing on Thursday, which is the first of three being held in a week.

Shares in Macquarie Bank dropped 3.86 per cent to $118.16.

It came after Wall Street stocks plunged Wednesday, with major indices losing more than 3 per cent in a sell-off prompted by the sudden jump in US interest rates and increasing trade worries.

When all the dust settled after a brutal session, the Dow Jones Industrial Average had lost 3.2 per cent or 830 points to finish at 25,498.74, in the biggest fall since February.

The broadbased S&P 500 slumped 3.3 per cent to end at 2,785.68, while the tech-rich Nasdaq Composite Index plummeted 4.1 per cent to finish the session at 7,422.05.

The Nasdaq decline was its worst in percentage terms since the surprise Brexit vote in June 2016.

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Losses were fairly broadbased, with tech companies Amazon and Microsoft down 6.2 per cent and 5.4 per cent respectively. Apple, Boeing, Nike and Visa all tumbled more than 4 per cent, while Caterpillar and 3M lost almost 4 per cent.

US stocks notched solid gains in the third quarter as investors brushed aside worries about trade wars and focused on strong corporate earnings and solid US economic data.

But stocks have been under pressure since the yield on 10-year US Treasury bonds jumped above 3 per cent last week, a sudden move that raised fears of an overheating economy, speeding inflation and more aggressive Federal Reserve interest rate increases.

“Fear is rising,” says chief investment officer at Cumberland Advisors David Kotok. “Investors are getting a wake-up call.”

“It’s shifting the tectonic plates,” said Jack Ablin, chief investment officer at Cresset Wealth Advisors. “Equity markets have enjoyed capital flows because bond yields have been so paltry. As rates move back towards fair value, capital is going to flow eventually out of equity risk taking.”

The turmoil came a day after the International Monetary Fund slashed its global growth forecast on worries about trade wars and weakness in emerging markets.

Tom Cahill of Ventura Wealth Management said investors were also unnerved by remarks from luxury company LVMH of a crackdown on some goods in China amid the country’s bitter dispute with the United States.

“Two weeks ago this kind of news would not have affected the market,” he said. “But since we are now in a corrective phase, any bad news accelerates the decline.”

LVMH’s travails also raised worries about whether the prospects of luxury brands are fading as the global economic outlook weakens. Among American brands, Tiffany slumped 10.2 per cent and Michael Kors Holdings fell 7.1 per cent.

US airlines were another big loser, with American Airlines sliding 5.8 per cent and Southwest Airlines 3.6 per cent as a major US hurricane caused flight cancellations in Florida.

Gina Martin Adams, the chief equity strategist for Bloomberg Intelligence, said investors were concerned about the big increase in yields, which makes it more expensive to borrow money.

She said they also fear that company profit margins will be squeezed by rising costs, including the price of oil.

Technology and internet-based companies are known for their high profit margins, and many have reported explosive growth in recent years, with corresponding gains in their stock prices. Ms Adams said investors have concerns about their future profitability, too.

That’s helped make technology stocks more volatile in the last few months. “As stocks go up, tech goes up more than the stock market. As stocks go down, tech goes down more than the stock market,” she said.