  The most abundant stars in the Galaxy, M dwarfs, are very commonly hosts to
diverse systems of low-mass planets. Their abundancy implies that the general
occurrence rate of planets is dominated by their occurrence rate around such M
dwarfs. In this article, we combine the M dwarf surveys conducted with the
HIRES/Keck, PFS/Magellan, HARPS/ESO, and UVES/VLT instruments supported with
data from several other instruments. We analyse the radial velocities of an
approximately volume- and brightness-limited sample of 426 nearby M dwarfs in
order to search for Doppler signals of cadidate planets. In addition, we
analyse spectroscopic activity indicators and ASAS photometry to rule out
radial velocity signals corresponding to stellar activity as Doppler signals of
planets. We calculate estimates for the occurrence rate of planets around the
sample stars and study the properties of this occurrence rate as a function of
stellar properties. Our analyses reveal a total of 118 candidate planets
orbiting nearby M dwarfs. Based on our results accounting for selection effects
and sample detection threshold, we estimate that M dwarfs have on average at
least 2.39$^{+4.58}_{-1.36}$ planets per star orbiting them. Accounting for the
different sensitivities of radial velocity surveys and Kepler transit
photometry implies that there are at least 3.0 planets per star orbiting M
dwarfs. We also present evidence for a population of cool mini-Neptunes and
Neptunes with indications that they are found an order of magnitude more
frequently orbiting the least massive M dwarfs in our sample.

Earth and Planetary Astrophysics