  Some of the citation advantage in open access is likely due to more access
allows more people to read and hence cite articles they otherwise would not.
However, causation is difficult to establish and there are many possible bias.
Several factors can affect the observed differences in citation rates. Funder
mandates can be one of them. Funders are likely to have OA requirement, and
well-funded studies are more likely to receive more citations than poorly
funded studies. In this paper this hypothesis is tested. Thus, we studied the
effect of funding on the publication modality and the citations received in
more than 128 thousand research articles, of which 31% were funded. These
research articles come from 40 randomly selected subject categories in the year
2016, and the citations received from the period 2016-2020 in the Scopus
database. We found open articles published in hybrid journals were considerably
more cited than those in open access journals. Thus, articles under the hybrid
gold modality are cite on average twice as those in the gold modality. This is
the case regardless of funding, so this evidence is strong. Moreover, within
the same publication modality, we found that funded articles generally obtain
50% more citations than unfunded ones. The most cited modality is the hybrid
gold and the least cited is the gold, well below even the paywalled.
Furthermore, the use of open access repositories considerably increases the
citations received, especially for those articles without funding. Thus, the
articles in open access repositories (green) are 50% more cited than the
paywalled ones. This evidence is remarkable and does not depend on funding.
Excluding the gold modality, there is a citation advantage in more than 75% of
the cases and it is considerably greater among unfunded articles. This result
is strong both across fields and over time.
