The reporting data of the Robert Koch Institute (RKI) backdated to the beginning of the disease show a clear bend from March 19 to 20. We have used this to better calibrate our models and to better understand the dynamics.

#### External activities

There was a slight decrease in out-of-home activity from March 8 to 15 and a strong decrease from March 15 to 22. We conclude the following:

1. The measures taken in Berlin on March 14th (school closures, closures of clubs, pubs, ...) have led to a sharp drop in school and leisure activities.
2. From about March 14 to about March 22, there was a further, very significant decline in activities, even without government orders.
3. The "contact ban" from 22.3. onwards has no effect in the data. Of course, we do not know whether without this measure the low level of external activities would have stabilised equally.

In addition, a slow drift back to more normal behaviour with regard to external activities can be seen from 25.3. Fig. 2, which refers to mobility behaviour instead of activity durations, confirms this interpretation.

On the basis of these data, we believe that the transmission of government instructions to changes in the infection dynamics was rather indirect: Large parts of society had come to the realisation that they had to reduce their activities outside the home, and this was already happening before the "contact ban" was ordered. State action accompanied and stabilised the adjustment that was taking place anyway, rather than preceded it. Similarly, it seems to be the case with the opening that is now taking place, which is "happening" anyway, and in a certain sense is being "followed" rather than "allowed" by state action.
