  We calculate Wilson loops of various sizes up to 20 loops in SU(3) pure
lattice gauge theory at different lattice sizes for Wilson gauge action using
the technique of numerical stochastic perturbation theory. This allows us to
investigate the perturbative series for various Wilson loops at high loop
orders. We observe differences in the behavior of those series as function of
the loop order. Up to $n=20$ we do not find evidence for the factorial growth
of the expansion coefficients often assumed to characterize an asymptotic
series. Based on the actually observed behavior we sum the series in a model
parametrized by hypergeometric functions. Alternatively we estimate the total
series in boosted perturbation theory using information from the first 14
loops. We introduce generalized ratios of Wilson loops of different sizes.
Together with the corresponding Wilson loops from standard Monte Carlo
measurements they enable us to assess their non-perturbative parts.
