In March 2020, in an attempt to slow the spread of Covid-19, several countries intervened by imposing strict lockdown measures that limited contact among people. In contrast, Sweden decided to not implement a mandatory lockdown and instead allowed people free choice on whether or not to follow the government recommendation to limit contact with others. Using the Synthetic Control Method, we estimate the causal effect of not implementing a mandatory lockdown in Sweden in the period from the end of February 2020 to the end of September 2020, a time when vaccines were as yet not available. We find that not imposing a mandatory lockdown resulted in a lower reduction of mobility and a substantial increase in mortality. Our results indicates that up to about 4411 of the 46554 deaths registered in Sweden during this period could have been avoided had Sweden implemented a mandatory lockdown. These results remain consistent when using two additional state-of-the-art estimation methods; the augmented synthetic control method and synthetic difference-in-difference.