There's a lot of data involved from a lot of different sources — which
introduces opportunities for error.
Not exact matches
This gives us a final
opportunity to spot check
for any formatting problems that may have been
introduced during the design process as well as a final check
for punctuation and other small
errors overlooked in the editorial process.
Adding to that some earlier periods means only that you
introduce new
opportunities for errors in the analysis — and making an
error in the analysis is, indeed, what you have done.