Handling 'NaN' values after merging data frames

I am creating a Recession Predictor project. I have 6 datasets (representing different things like unemployment rate) and a total of 16 columns. I cleaned the data and merged on the month and year columns. Problem is that one of the datasets was from 1947-2022, one from 1950-2022, a few from 1960-2022 and 1970-2022 and one from 1990-2022. The one from 1990-2022 has 10 columns/features while the other datasets just had one column/feature besides the month and year columns. Now, …

data datascience merging nan values