On Wall Street this month's falls have effectively erased all the gains made for the year to date.
In Asia markets have been hit even harder. The Shanghai Composite Index is now in bear territory - off by more than 20 per cent this year.
The falls also took the broader MSCI Asia Pacific Index - which includes shares from the NZX and ASX - into bear territory.
Bloomberg has estimated that about US5$trillion has been knocked off the value of the MSCI Index in the year to date.
Investor fears have escalated in the past few weeks - albeit over a number of issues that have been well flagged for the past year.
US interest rates are on the rise, raising costs for indebted companies and making returns from safer investments like bank deposits more attractive.
Trade tensions are dampening expectations for global growth with China and its trading partners being hit particularly hard.
The New Zealand and Australian markets seem to have been caught in the fallout.
The ASX is also down more than eight per cent for October — and 10 per cent since August.
NZX-50 heavyweight A2 Milk is heavily reliant on the Chinese market. It fell close to two per cent yesterday and is off almost 30 per cent from its high above $14 a share in March.
There are also fears in the US that the shine is coming off President Donald Trump's tax-cut fueled economic boom.
Sales of new US homes fell 5.5 per cent in September, the fourth monthly drop.
It is also reporting season in the US and several major companies have delivered downbeat outlooks.
Rising fuel prices are also starting to bite and stoke inflation fears.
Trump this week turned on the US Federal Reserve, with a direct and highly unorthodox attack on chairman Jerome Powell. He blames the Fed for causing the slump by raising interest rates.
Ironically rates are on the rise because parts of the US economy - such as employment and consumer confidence - have been so strong.
Local tech companies led the NZX 50 lower on very light volumes. Gentrack dropped 3.5 per cent to $6.58 and Pushpay fell 2.8 per cent to $3.48. A2 Milk is another momentum stock whose rapid gains in recent years have given it a bigger weighting on the index. It fell 2 per cent to $9.90.
"It's not fundamentals driving things at the moment - investors are selling because other equity markets are in decline," said Grant Williamson, a director at Hamilton Hindin Greene.
Freightways fell 2.1 per cent to $7.13 on modest volumes after the courier and information management firm said first-quarter revenue was up 8.3 per cent. It also affirmed expectations for earnings growth.
Williamson said New Zealand's economic fundamentals are still standing up pretty well.
"There are still good quality companies - they've just got a bit cheaper."
Spark New Zealand was the most traded stock, on a volume of 3 million. It fell 0.7 per cent to $3.835, while Meridian Energy was down 0.3 per cent to $3.07 on more than twice its normal volume. Z Energy fell 0.7 per cent to $5.85 on more than three times its average volume.
Air New Zealand dropped 2.4 per cent to $2.615 with 1.5 million shares traded, slightly more than usual. Rival Qantas Airways today said first-quarter revenue rose 6.3 per cent, helping offset higher fuel costs.
Metlifecare rose 1 per cent to $5.91 after buying land to expand its Botany development in Auckland. Rival Ryman Healthcare gained 1.5 per cent to $11.77 on almost twice its average volume.
Among other stocks with more than 1 million shares traded, Contact Energy slipped 0.2 per cent to $5.52, Fletcher Building was unchanged at $5.71, Sky Network Television slipped 0.9 per cent to $2.30 and Mercury NZ declined 1.2 per cent to $3.33.
Heartland Bank fell 2.6 per cent to $1.52 on a volume of 1.3 million shares, almost four times its 90-day average.
Outside the benchmark index, Steel & Tube fell 2.9 per cent to $1.32 after chair Susan Paterson was re-elected at today's annual meeting. Paterson revealed the company had investigated buying Fletcher assets, which was why the board was wary of regulator concerns when it batted away a takeover offer from the larger firm.
Scott Technology was unchanged at $2.90 after reporting a 12 per cent increase in operating earnings as it bedded in new acquisitions.
South Port New Zealand was unchanged at $7.40 after affirming expectations for annual profit to fall 10 per cent; TeamTalk gained 1.2 per cent after affirming flat earnings for the current financial year.
Dual-listed AMP dropped 18 per cent to $2.93 on the NZX. The Australian financial services firm will sell its AMP Life unit for A$3.3 billion and plans to spin out its New Zealand wealth management and advisor business as a separately listed company in an initial public offering.
