We have to rely on models and econometric methods to estimate it. And the estimated level varies greatly depending on the method and data used. On top of that, it can often only be gauged with very wide uncertainty bands.
[…] an agency’s sense of mission […] should not be “polluted” through considerations that can be dealt with  https://www.bundesbank.de/en/press/speeches/combating-climate-change-what-central-banks-can-and-cannot-do-851528  5/8  20/11/2020  Combating climate change – What central banks can and cannot do | Deutsche Bundesbank  [using] other, proper instruments.” Otherwise, central banks will soon face calls to correct market outcomes in other areas as well.