Britain’s economy lost another half a million working days to strikes in March amid the most severe round of industrial action in nearly four decades.

The UK has now lost more than 3.5 million days to walkouts since the Office for National Statistics began collecting the data last June following a pause during the Covid pandemic.

The ONS said Tuesday that 556,000 days were lost due to March’s industrial action, up from 332,000 in February, and the highest figure for the month since 1984.

Workers across the UK have been striking in a bid to maintain their spending power, which has been eroded by stubbornly high double-digit inflation.

Junior doctors held a 72-hour walkout in March, their first industrial action since 2016. Other NHS staff, such as ambulance workers and nurses, had paused strikes to engage in talks with the government. Since then, a pay offer was agreed with most unions — however, the Royal College of Nurses is demanding a higher raise and could announce more strikes.

Average regular pay growth was 7% for the private sector and 5.6% for the public sector in January to March 2023, the ONS also said Tuesday. Public sector pay growth has not been higher since August to October 2003.

The Centre for Economics and Business Research estimated last week that industrial action cost the economy £243 million ($304 million) in the first quarter — lower than in the final months of 2022 when walkouts on the rail network and at Royal Mail were even more frequent.

Read More: UK Nurses Can Get Bigger Pay Hike by Striking Again, Says Union

Industrial action has shifted toward the education sector this year after some rail unions resolved their pay disputes. Since Covid, schools have become more adept at remote teaching, reducing knock-on economic costs as fewer parents were forced to cancel work.

On Monday, teachers and consultants in the NHS started voting over whether to strike again. Meanwhile, Britain’s rail network ground to a halt over the weekend as the RMT and Aslef unions walked out over pay, disrupting travel plans for visitors to Liverpool during the final of the Eurovision song contest. Further rail strikes are planned for the summer.

--With assistance from Tom Rees.

(Updates with wage growth figures in sixth paragraph.)