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The announcement by Apple and Google (Report, September 2) that they will include Covid-19 tracking features in their smartphone operating systems is helpful to public health authorities around the world. Now users no longer need to download an application; it’s just there when the operating system is updated.
Freedom of choice is preserved, because users still have to choose to use the application and the unlucky ones who are infected still have to register this fact with the application for the contact process to be triggered.
However, again, we give the freedom to the algorithms behind this. We no longer need to download the app, but we must trust that Apple and Google have come up with the correct algorithms to infer the distance from the Bluetooth signal strength.
For readers inclined to mathematics, there are many articles on this topic, the summary of which is that inferring distance is really difficult. Phones are carried in pockets, bags, on their side, upside down, or placed on tables; Phones have different sensitivities to Bluetooth radio signals. The imputation of distance requires a lot of probability and processing.
Apple and Google may have done wonderful technical work here. As with everything algorithmic, an act of trust is required. This trust could be well placed. One step towards this confidence would be if the algorithms and test results could be published in their entirety. Let’s look at the math, let’s look at the algorithms, let’s understand the system that is now part of our smartphones.
Michael Hobbs
Founder, Reputable Ventures,
London N13, UK
