are subgroups necessary

[liquid]

When you divide automatically years by categories FET creates subgroups also. Are they necessary if I do not use them in activity assignments?

[Volker Dirr]

They are needed, even if you dont need them. Maybe just do a small sample to see what happen if you remove the subgroups. Fet is not able to understand the dataset correct and will generate false tables if you remove the subgroups.