The week between Christmas and New Year is the hardest time to acquire users but the most potentially lucrative time too.

This is according to data from ad firm Nanigans, which studied advertising data on Facebook during November and December 2015 and compared various key metrics against the averages of the two months combined.

It found that installs and in-app purchases saw a sharp increase in the week following Christmas. Installs increased to 17% above the average for both months combined, while in-app purchases saw an increase to 22% above the average.

However, click-to-install and click-to-purchase rates dropped off at the same time to 13% below average. Click-to-purchase rates also dropped to 9% below average.

Be thankful

During the week of Thanksgiving however click-to-install rates climbed to 33% above average, while click-to-purchase rates increased to 32%.

Advertisers already appear to be aware of these trends. Ad spend increased to 3.4% above the average during the week after Christmas, and saw a small 0.7% increase over the average during Thanksgiving week.

And the ads themselves increase in price along with the spends. CPMs on Facebook were found to be 49% higher than the average on the week of Christmas, and 50% higher than average during Thanksgiving week.

Despite all this, click-through rates do not change very much. The biggest change is an increase to 0.16% above average two weeks before Christmas, but no other change comes in at above 0.1%.