Why are the big ASX mining share prices slipping today?

The share prices of ASX mining giants BHP Group Ltd (ASX: BHP), Rio Tinto Limited (ASX: RIO) and Fortescue Metals Group Limited (ASX: FMG) are in the red today.

However, the share prices of all three major iron ore miners have slipped by less than 1% at the time of writing.

Moody's Investors Service analysts expect the global metals and mining industry's earnings before interest, tax, depreciation and amortisation (EBITDA) to increase 30% through early 2022. But S&P Global reported the market value of all three miners fell through March.

BHP's market capitalisation fell by 8.5%, Rio Tinto's fell by 10.6%, and Fortescue's fell by a substantial 17% from February to March. The Newcrest Mining Ltd (ASX: NCM) market cap also fell by 1.8%. 

Moody's bullish on miners despite falls

The market value declines weren't limited to Australian companies. They were largely replicated across the global industry, with Chinese heavyweights Zijin Mining Group and China Molybdenum falling by double digits.

S&P reported that overall, 11 of the largest 25 companies in the metals and mining sector decreased in market value during March. In brighter news for miners, every single company in the top 25 index had gained on its market value 12 months prior.

Moody's believes the mining industry will continue to see revenue growth due to consistently high materials demand, as the global economy invests in stimulus measures following the coronavirus pandemic.

"The positive outlook for the global metals and mining industry stems mainly from rising demand and tight supplies for steel, iron ore and copper as economic activity picks up in the wake of the pandemic," Barbara Mattos, a Moody's senior vice president, said.

"Aluminum, nickel and zinc will remain in surplus in 2021, with aluminum seeing a slow recovery, while nickel and zinc supplies will grow as production levels normalise."

Rio Tinto, BHP and Fortescue share price snapshots

At the time of writing, the BHP share price is falling 0.92% to $46.24 per share. It has gained nearly 10% in 2021 so far.

Rio Tinto's share price is also down slightly to $115 per share, after gaining just over 1% in 2021. Fortescue is the only miner of the three that has increased its share price this month, up 0.5%.

However, it's also posted the only loss in 2021, down more than 10%. The Fortescue share price is also falling today and is down 0.86%.