The market capitalisation of Western Australian listed companies have crashed to a 20-month low over September, falling 21 per cent to $127 billion, according to the Deloitte WA Index.
The figure compares to an 11.2 per cent decline by the All Ordinaries index over the same period.
"The Deloitte WA Index lost $34 billion in the month of September, considerably worse than other major indices," Deloitte Perth managing partner Keith Jones said.
"The stocks in the mining industry recorded the most significant falls with a cumulative fall of 27.62 percent within the Index."
Movers and shakers during the month of September within the index included Portman Ltd, St Barbara Ltd and Extract Resources Ltd.
Portman Limited recorded a gain of 14.21 percent in market capitalisation in September, driven by a takeover offer by majority shareholder Cleveland-Cliffs.
"St Barbara Limited and Extract Resources Limited also recorded gains during the month with their market capitalisation increasing by 34.88 percent and 19.79 percent respectively," said Mr Jones.
St Barbara's gain was in response to the signing of a new joint venture and option agreement with Rubicon Resources Ltd while Extract's lift follows a merger announcement with Kalahari Minerals plc.
Included in the top 10 WA stocks for the index were Woodside Petroleum Ltd, Wesfarmers Ltd, Fortescue Metals Group Ltd, Aquila Resources Ltd and West Australian Newspapers Holdings Ltd.
In contrast to August, the major world indices fell significantly in September.
The US S&P 500 fell 14.94 percent due to further tightening and instability in the credit markets, corporate collapses within the banking sector and renewed speculation of a recession.
This was closely followed by the Nikkei, the FTSE 100 and the Australian All Ordinaries which recorded losses of 13.87 per cent, 13.34 per cent and 11.20 per cent respectively.
The commodities market also fell in September with prices of palladium and platinum falling by 34.90 per cent and 31.99 per cent respectively.
Both metals have fallen on the back of concerns over future demand from the US Automotive industry. Gold recorded the only gain up 4.79 percent from August with investors seeking a safe haven for value.
