**4. Conclusions**

It has been verified that, in the period 2000–2016, there is a predominance of documents written in multi-authorship in the categories *Demography* and *Urban Studies*. Likewise, the number of documents in collaboration has been increasing proportionally to the total production. The highest values in the collaboration indicators, DC, CI have been reached in the most recent years, showing a tendency to continue increasing. This increase in the number of citations in relation to the increase in the number of authors per article shows a similar pattern to those found for other branches of knowledge closer to the hard sciences.

Despite these results, the international collaboration is not so high, compared to author collaboration, which means that a great portion of the multi-authored documents are written by authors affiliated to institutions of the same country.

The analysis of the scientific production of these two scientific categories in social sciences, *Urban studies* and *Demography*, has confirmed the findings of previous studies [44, 45] stating international collaboration in science is growing rapidly. This international collaboration has a correlation with the increase in the citation of multi-authored publications. The internationalisation of science in these two categories is largely due to the collaboration of researchers from the USA, England and Canada.
