  We present a polarization catalog of 533 extragalactic radio sources with 2.3
GHz total intensity above 420 mJy from the S-band Polarization All Sky Survey,
S-PASS, with corresponding 1.4 GHz polarization information from the NRAO VLA
Sky Survey, NVSS. We studied selection effects and found that fractional
polarization, $\pi$, of radio objects at both wavelengths depends on the
spectral index, source magnetic field disorder, source size and depolarization.
The relationship between depolarization, spectrum and size shows that
depolarization occurs primarily in the source vicinity. The median $\pi_{2.3}$
of resolved objects in NVSS is approximately two times larger than that of
unresolved sources. Sources with little depolarization are $\sim2$ times more
polarized than both highly depolarized and re-polarized sources. This indicates
that intrinsic magnetic field disorder is the dominant mechanism responsible
for the observed low fractional polarization of radio sources at high
frequencies. We predict that number counts from polarization surveys will be
similar at 1.4 GHz and at 2.3 GHz, for fixed sensitivity, although $\sim$10% of
all sources may be currently missing because of strong depolarization. Objects
with $\pi_{1.4}\approx \pi_{2.3} \ge 4\%$ typically have simple Faraday
structures, so are most useful for background samples. Almost half of flat
spectrum ($\alpha \ge -0.5$) and $\sim$25% of steep spectrum objects are
re-polarized. Steep spectrum, depolarized sources show a weak negative
correlation of depolarization with redshift in the range 0 $<$ z $<$ 2.3.
Previous non-detections of redshift evolution are likely due the inclusion of
re-polarized sources as well.
