Typically you do both, keep a log and keep a current table (you wouldn't recalculate every time. As for space, you archive in a regular basis (say every year).

Typically you do both, keep a log and keep a current table (you wouldn't recalculate every time. As for space, you archive in a regular basis (say every year). That's why you cannot check you're bank statement from 2 or 3 years ago.