New daily infections have fallen by 31% over the last seven days, causing some consternation and head-scratching in the epidemiological modelling community.
Neil Ferguson, for example, had claimed only ten days ago that cases reaching 100,000 per day was “almost inevitable”. Yesterday he backtracked, noting that “the equation has fundamentally changed”. (One hopes he was referring to the equations in his model.)
As to why daily infections have been falling, some epidemiologists have said the full effects of ‘Freedom Day’ are yet to appear in the data. ‘Freedom Day’, you will recall, was when some remaining lockdown measures were lifted on the 19th of July.
Yesterday, the Prime Minister told reporters, “Step Four of the opening-up only took place a few days ago, people have got to remain very cautious and that remains the approach of the Government.”
Aside from the fact that ‘Freedom Day’ was nine days ago, and you’d expect any effects to show up by now, there’s another indicator suggesting that a rebound in cases is unlikely – the Google mobility index.
Google publishes regular reports on the level of mobility in most of the world’s countries, based on smartphone data. Looking at the latest U.K. numbers, there is no evidence of any change in behaviour caused by ‘Freedom Day’.
The chart below shows the retail mobility index. (Numbers are percentage changes relative to the baseline; ‘Freedom Day’ is marked with a red line.) As you can see, there was no sudden increase on the 19th of July.
The next chart the residential mobility index. Once again, there was no sudden decrease on the 19th of July. (And the other four sub-indices show the same pattern.)
Of course, the Google mobility index isn’t a perfect guide to behaviour. And given that rapid decreases in case numbers have occurred in the absence of mobility changes, it’s possible that rapid increases could too. Nonetheless, these figures suggest that daily infections aren’t about to rebound, and we don’t need to “remain very cautious”.