Statistics in relation to social housing stock are gathered by the National Oversight and Audit Commission (NOAC) in their annual reports on Performance Indicators in Local Authorities. These reports provide a range of information in relation to social housing stock including the total number of dwellings in each local authority area, broken down between the level of units provided directly and through the various schemes in operation.
The most recent NOAC report available is for 2015, which is available at the following link:
http://noac.ie/wp-content/uploads/2016/12/2015-PI-Report.pdf.
Table 2 of the report shows that the number of units owned by Galway City Council as at 31 December 2015 was 2,307.