dmrktrading

1. In time series regressions, it needs to be mean reverting, which means b0+b1=1. There are several other rules about bias in the procedures and results of time series.

In regular linear least-squares regression (like a scatter-plot, not time series), the sum of the SQUARED residuals will be zero, but this doesn't really have anything to do with bias--it's sort of the definition of what line you're going to fit. (Although not in the curriculumn, an alternative would be fitting a line that minimizes the absolute value of the residuals instead.)