Closing schools and child care centres for three months would have cost the economy $34 billion, Treasurer Josh Frydenberg said.
The figure was based on 1 million adults needing to withdraw from the workforce to look after their children at home, he told the Press Club in a speech that emphasised the economic "cliff face" on which Australia had stood as the number of coronavirus cases rose quickly in March.
The federal government is desperate to get schools operating to help get the economy moving again, but has run into resistance from some jurisdictions, including the ACT - which hasn't announced a timetable for students to return to school - and Victoria. Other states are staging returns from May 11.
On Friday, the government will begin easing restrictions, allowing some businesses to reopen, with the details yet to be announced.
Mr Frydenberg said schools and childcare centres were not just big employers but were "important enablers for the broader economy". Transport and logistics were in the same category because of their impact on supply chains.
We are in a harvesting phase during which we will look at new and old reform proposals with fresh eyes.Treasurer Josh Frydenberg
"We must get people back into jobs, and we must get people back at work," he said. "For every extra week that the current restrictions remain in place, Treasury estimates that close to $4 billion will be reduced in economic activity, from a combination of reduced workforce participation, reduced productivity, and reduced consumption."
Once businesses were reopened, they should stay open. That meant making sure consumers were confident to use businesses and businesses were confident that they would not be forced to close again, he said.
"When businesses reopen after a forced hiatus, many have to restock, absorbing their remaining working capital. This reinforces the need [to have] the right processes and protocols in place to manage the health risk and provide for a safe working environment," he said.
Asked whether the government was still considering tax cuts, Mr Frydenberg avoided the question of personal tax cuts, but suggested that company tax cuts were in his thinking.
Australia's business tax rate was uncompetitive for big companies and the second highest in the OECD, he said. Companies paid 30 cents in the dollar, compared with 21 cents in the United States and 19 cents in Britain.
"Tax rates, like flexible workplaces, like infrastructure, like deregulation, they are all key factors that businesses consider when they establish their businesses around the world, but also when they decide to hire more people," he said.
"Capital is mobile. Business is not very sentimental, and so we have to ensure we have the most competitive environment possible."
Mr Frydenberg said the government was "not about to announce a shopping list of reforms".
"We are in a harvesting phase during which we will look at new and old reform proposals with fresh eyes," he said.
The government would focus on "practical solutions" including improving skills, he said. He also promised new infrastructure projects to maintain the $100 billion 10-year pipeline and regulatory reform for businesses, tax and industrial relations reform.
The principles behind Coalition reforms in the past would be the same for the coronavirus recovery, he said - "encouraging personal responsibility, maximising personal choice, rewarding effort and risk-taking while ensuring a safety net", with job creation coming from the private sector not the government.
Mr Frydenberg said Australia must guard against protectionist sentiment and remain a trading nation.
By Tuesday, 725,000 businesses had applied for the JobKeeper wage subsidy for more than 4.7 million workers, he said.
Deloitte Access Economics Chris Richardson said the economic picture was "truly horrendous".
"The global financial crisis was a storm in a teacup by comparison," he said.
Unemployment would not return to the pre-virus rate until late 2024, he said. The unemployment rate was 5 per cent in February and is forecast to double to 10 per cent by June.
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