I currently have a micro (5 years) panel data of house price transaction. There are a total of 800 different high rise properties (name of apartment/condo) and 30000 transactions across the 5 years. However, the data is really unbalanced as residential properties have different numbers of transaction in a year. Also at times, a particular year does not have transaction of a particular property.

I am unsure as how I should proceed with the analysis. If possible, I would like to avoid the pathway of removing the non-repeated properties from the data.