People living in poorer areas of the country were more likely to be out and about during last year's level 4 lockdown, putting themselves at greater risk of exposure to COVID-19, new research has found.
Before the lockdown, which began in late March, it was people at the other end of the spectrum - those living in the richest areas - that had the greatest mobility, analysis of cellphone location data shows.
"A key interest of mine, for many years, has been the role of inequality in society and how this leads to adverse consequences," said Associate Professor Malcolm Campbell of the University of Canterbury. "Not just for those individuals at the raw end of any inequality, but for society as a whole."
Researchers at Canterbury, the Ministry of Health and Denmark's Aarhus University divided the country into 2253 areas, sorting them into five different groups depending on their level of deprivation according to the 2018 census. They overlaid that with hourly mobile phone location data.
"Prior to the implementation of a national lockdown, under no movement restrictions, the highest population mobility was in the least-deprived quintile areas," the study, published in the Journal of Epidemiology and Community Health on Wednesday, said.
Movement in all five quintiles started to drop a week before the country went into level 4 - the toughest in our four-level COVID-19 alert system. People in the wealthiest areas cut their movement right back, while those in the most deprived didn't drop nearly as much.
"While the least deprived areas experienced the highest movement under no restrictions, the most deprived areas were the most mobile immediately after level 4 restrictions were introduced - the unequal social impacts of 'lockdown' writ large," the study said.
Towards the end of level 4, movement amongst most groups started to increase - most notably those in the bottom quintile, whilst movement in the wealthiest areas stayed flat right through level 3, with no noticeable increase until the much less-restrictive level 2.
By the time the country went into level 2 in mid-May, people in the most-deprived areas were moving around as they did before the lockdown, while those in the least-deprived areas still showed signs of staying at home.
"Mobility in the less-deprived quintile areas remained lower than pre-lockdown, whereas the more-deprived areas increased beyond that of pre-lockdown - an unequal recovery from 'lockdown'."
The researchers said there were various possible explanations, but the most likely was that people in poorer areas tend to be 'essential' workers - in supermarkets and public transport, for example - who can't do their jobs from home. They were also perhaps more likely to make frequent shopping trips during the lockdown, financially unable to stock up ahead of time.
"An alternative explanation is that [the most deprived] areas have the highest proportion (29 percent) of supermarkets per quintile across the country, compared with only 11 percent being located in [the least deprived] areas. This would be a likely motivation to increase mobility into [the least deprived] areas."
People in the most-deprived areas are also less likely to be able to take time off work, they said.
"Conversely, the less-deprived neighbourhoods are more likely to be populated with higher paid 'professionals' who may be able to work from home or shield themselves with pre-existing capital, hence reducing movement.
"We favour the explanation that it is occupation differences that exacerbate daily movement during the lockdown."
The researchers said the study shows "a one-size policy does not fit all neighbourhoods".
"If the policy worked the same everywhere, you would expect the [pre-lockdown] pattern to stay exactly the same, just decrease," said Prof Campbell, saying the research shows "those with sufficient means can self-isolate, buffered often by their income, while those without cannot and are therefore at higher risk of infection and subsequent mortality".
When New Zealand moved to level 1, the study shows movement in all groups rose above where it was in February - reflected in the record rise in GDP that happened in the third quarter.