  Galaxy mergers and interactions are an integral part of our basic
understanding of how galaxies grow and evolve over time. However, the effect
that galaxy mergers have on star formation rates (SFR) is contested, with
observations of galaxy mergers showing reduced, enhanced and highly enhanced
star formation. We aim to determine the effect of galaxy mergers on the SFR of
galaxies using statistically large samples of galaxies, totalling over
200\,000, over a large redshift range, 0.0 to 4.0. We train and use
convolutional neural networks to create binary merger identifications (merger
or non-merger) in the SDSS, KiDS and CANDELS imaging surveys. We then compare
the galaxy main sequence subtracted SFR of the merging and non-merging galaxies
to determine what effect, if any, a galaxy merger has on SFR. We find that the
SFR of merging galaxies are not significantly different from the SFR of
non-merging systems. The changes in the average SFR seen in the star forming
population when a galaxy is merging are small, of the order of a factor of 1.2.
However, the higher the SFR above the galaxy main sequence, the higher the
fraction of galaxy mergers. Galaxy mergers have little effect on the SFR of the
majority of merging galaxies compared to the non-merging galaxies. The typical
change in SFR is less than 0.1~dex in either direction. Larger changes in SFR
can be seen but are less common. The increase in merger fraction as the
distance above the galaxy main sequence increases demonstrates that galaxy
mergers can induce starbursts.
