|TRIVAGO N.V. filed this Form 6-K on 02/06/2019|
increase in Americas was driven by slightly improved levels of commercialization and slightly improved traffic quality. These effects were partly offset by unfavorable foreign exchange rates of certain Latin American currencies against the euro and a shift towards lower RPQR locales, particularly away from the North America. The increase in Developed Europe was due to a significant improvement in traffic quality. The increase in RoW was primarily driven by slightly improved traffic quality while it was negatively impacted by a shift towards lower RPQR locales.
During the twelve months ended December 31, 2018, RPQR decreased by 10% and 3% in Americas and RoW, respectively, while it increased by 7% in Developed Europe as compared to the same period in 2017. Consolidated RPQR decreased by 4% and was driven by decreased RPQR in Americas and RoW. The decline in Americas was due to lower levels of commercialization particularly in the first nine months of 2018, a shift towards lower RPQR locales in the second half of 2018 and the negative foreign exchange effects described above, partly offset by slightly improved traffic quality. The decline in RoW was driven by lower commercialization and the negative foreign exchange effects described above, partly offset by slightly improved traffic quality. The increase in Developed Europe was driven by positive effects of improved traffic quality, partly offset by the negative impact from lower levels of commercialization in the first nine months of 2018.
Return on Advertising Spend
We track the ratio of our Referral Revenue to our Advertising Spend, or ROAS. We believe that ROAS is an indicator of the effectiveness of our advertising and it is our primary operating metric.
The following table sets forth the ROAS for our reportable segments for the periods indicated:
Consolidated ROAS improved to 162.6% in the fourth quarter of 2018 and to 123.0% in the twelve months ended December 31, 2018, respectively, compared to 118.4% and 115.3% in the same periods in 2017.
ROAS improved by 36.0 ppts, 65.5 ppts and 33.8 ppts in Americas, Developed Europe and RoW, respectively, in the fourth quarter of 2018, compared to the same period in 2017. As noted above, we continued to optimize our Advertising Spend since the second quarter of 2018 and made significant reductions across all segments in order to improve profitability. These reductions were implemented across all segments and resulted in