When the index was launched in mid-2000, the top 10 companies were half mining and energy.
The top 10 companies by market capitalisation back then were Wesfarmers, Woodside Petroleum, Homestake Mining, Bank of Western Australia, Foodland Associated, Franked Income Fund, Videlli Corporation, Seven West Media, Iluka Resources, and Orbital Corporation.
"Fast forward 20 years and the diversification almost vanishes. Apart from Wesfarmers and Woodside, all other top 10 companies at 30 June 2020 are in the metals and mining sector," Deloitte WA Audit and Assurance partner Dave Andrews said.
At June 30, 2020 the top 10 is was Wesfarmers, Fortescue Metals Group, Woodside, Northern Star Resources, South32, Saracen Mineral Holdings, Mineral Resources, Iluka, IGO, and Regis Resources.
Wesfarmers, which owns a large WA lithium deposit, has been in either top or second spot for the entire two decades, only occasionally losing the top spot early in the index to Woodside.
Earlier this month, FMG overtook Wesfarmers as WA's most valuable company.
Andrews noted the rise of WA-based gold companies in the Index.
"With four producers in the top 10, and 10 gold-focused companies occupying the top 20, the importance of gold to the WA Index cannot be ignored," he said.
"It's a well-known fact gold is considered a safe-haven asset in times of economic uncertainty, and with Brexit, the US/China trade wars, and a global COVID-19 pandemic, we are not surprised to have seen investors flock to add gold exposure to portfolios over recent years."
Deloitte also announced the winners of its High Growth Awards for 2020, which are usually presented at Diggers & Dealers.
Unsurprisingly all six of this year's winners are from the gold sector.
The biggest mover in the WA Index was De Grey, which saw a 3123% increase in its market capitalisation to A$1.06 billion, and climbed from 232rd on last year's list to 19th.
Ramelius Resources and Perseus Mining were also big movers, with their market caps up by 236% and 124%, respectively.
The biggest movers in the top 100 were Musgrave Minerals, up 954% to $216 million, Chalice Gold Mines, up 844% to $302 million, and Rox Resources, up 824% to $167 million.