  In solo research, scientists compete individually for prestige, sending clear
signals about their research ability, avoiding problems in credit allocation,
and reducing conflicts about authorship. We examine to what extent male and
female scientists differ in their use of solo publishing across various
dimensions. This research is the first to comprehensively study the 'gender
solo research gap' among all internationally visible scientists within a whole
national higher education system. We examine the gap through 'individual
publication portfolios' constructed for each Polish university professor. We
use the practical significance/statistical significance difference (based on
the effect-size r coefficient) and our analyses indicate that while some gender
differences are statistically significant, they have no practical significance.
Using a partial effects of fractional logistic regression approach, we estimate
the probability of conducting solo research. In none of the models does gender
explain the variability of the individual solo publishing rate. The strongest
predictor of individual solo publishing rate is the average team size,
publishing in STEM fields negatively affects the rate, publishing in
male-dominated disciplines positively affects it, and the influence of
international collaboration is negative. The gender solo research gap in Poland
is much weaker than expected: within a more general trend toward team research
and international research, gender differences in solo research are much weaker
and less relevant than initially assumed. We use our unique biographical,
administrative, publication, and citation database ('Polish Science
Observatory') with metadata on all Polish scientists present in Scopus
(N=25,463) and their 158,743 Scopus-indexed articles published in 2009-2018,
including 18,900 solo articles.
