A new tax was implemented to discourage the purchase of holiday homes, and has led to a decline in second homes in popular tourist areas.
Gwynedd owned 4,720 second homes last year, compared to 5,098 in 2013.
In response to claims that people were priced out of their communities, the council introduced a 100% council tax premium for second homes.
The policy "acts as a disincentive to buying or owning a second home within the area".
It also attributes 7.4% of the fall to second-home owners who apply to have their properties reclassified to "a self catering holiday unit".
Gwynedd charges a 100% premium for 3,746 homes. Swansea has 1,284, and Pembrokeshire has 3,794.
Anglesey and Flintshire charge 50% currently, while Conwy charges a 25% premium.
Labour First Minister Mark Drakeford and Plaid Cymru leader Adam Price both announced a new policy in their parties' cooperation agreement. This gives local authorities the power limit second homes or holiday lets.
A spokesperson for Gwynedd said that "As a council we are working closely together with the Welsh government in order to develop new measures control the number holiday homes within the area."
According to the council, it wanted to "prevent second-home owners from changing their status to avoid paying the council's tax premium and increase the number houses available for local people at an affordable cost".
The Welsh government also shows mixed results for councils that charge a 100% premium for second homes.
Pembrokeshire saw an increase in second homes, going from 4,068 in 2002/22 to 4,216 this past year.
There was a drop in second homes in Swansea from 2,104 to 1,585 between those two periods.
Cymdeithas yr Iaith Gymraeg, a Welsh language campaign group, stated that second homes were "only part of the housing crisis."
It is calling for legislation to guarantee that local residents have the right to own a home.
Jeff Smith, chair of the sustainable communities group of the group, stated that "there is public support to such measures."
