You would gather 2020 data on that rental, to see if there is any loss or income. The damage that resulted in lost rental activity in 2019 may not have carried into 2020. If you don't prepare 2020, you don't how 2019 impacts that activity or what carries over to 2021. That's why I used the word "continuity" as in, the activity continued over all these years, so each year gets evaluated and is a link in the chain.