Australia's biggest winners and losers

Summary: Which company has been the biggest gainer over the last year, and who has been the biggest loser?

Key take-out: The major banks have been hit hard, collectively losing billions.

Australia's four major banks have collectively lost almost $34 billion in market value over the past year, led by a $16 billion plunge in the market value of our biggest company – Commonwealth Bank.

But the biggest single loss in company value over the past year was outside of the financial sector. It was reserved for telecommunications giant Telstra, which in just 12 months lost over $19 billion of its market worth, while its share price fell more than 37 per cent.

Research by InvestSMART of Australia's list of top 20 companies by market capitalisation shows a wide range of moves up and down the ladder from June 1, 2017 to June 1 this year.

It wasn't all bad news among the biggest companies either. Mining behemoth BHP and blood products group CSL both rose up the top 20 ranks, collectively adding on almost $54 billion in market value.

By contrast, the big banks have been among the worst performers for investors over the last 12 months, and most expectations are that values will deteriorate as a combination of market factors bite further into their revenues and profits margins.

These include the effects of the slowing housing market, tighter lending conditions and slowing credit growth, increased market competition, and higher regulatory risks flowing from the banking Royal Commission.

For investors heavily exposed to the Australian banking sector because of their fully franked dividends, expect the year ahead to be volatile.

Commonwealth Bank's market capitalisation at June 1 was just under $122 billion, compared with $138 billion at the same time last year, while the next biggest value fall among the banks was recorded by NAB, which lost just over $7.6 billion.

NAB fell two places on the top 20 ladder as its market value dropped from $80.6 billion to $72.9 billion, while Westpac also slipped a place as its value dropped $7 billion from $102 billion to $95 billion.

By contrast, solid performance gains pushed Macquarie Group higher through the year, adding more than $8 billion to its value.

Also in the financial services sector, AMP suffered a $3.4 billion erosion in its market value, from $14.8 billion to $11.4 billion, keeping it in 20^th position. Meanwhile, insurer QBE dropped out of the top 20 from 16^th position previously as its value fell $4.8 billion from $17.7 billion to $12.9 billion.

Yet fellow insurer Insurance Australia experienced solid gains in the period, rising $4.2 billion in value from $15 billion in 2017 to $19.2 billion.

Poor business performance, coupled with heightened market competition, saw Telstra slip four places from seven to 11 as its value dropped from $52.3 billion to $33.3 billion.

Fuelled by higher commodity prices and operational gains, BHP was the biggest gainer. It jumped from fifth spot on the ladder in 2017 to second as its market value surged by $28.6 billion from $76.8 billion to $105.3 billion.

Rival miner Rio Tinto, which is worth roughly a third of BHP, gained $7.6 billion in the year from $26.6 billion to $34.2 billion. And entering the top 20 ranks was South32, which gained more than $5 billion in value, taking 16^th position with a market worth of $19.1 billion.

CSL continued to benefit from higher global demand for its products, with its market worth rising $25.3 billion from $58.7 billion to $84.1 billion. It is now Australia's fourth largest company by market value.

Further down the list, retailers Wesfarmers and Woolworths both recorded similar gains in market value, adding $3.24 billion and $3.66 billion respectively.