This year, we invested more than $4 billion in Europe on infrastructure, programs, people, and new tools and services to help you build your brands and grow your businesses. With these investments, we expanded Free One-Day Delivery to more than six million Prime-eligible items. We are thrilled with the response of our mutual customers and want to thank you for your continued innovation in providing unique selection at low prices.
We're announcing an upcoming referral fee promotion and adjustments, Fulfillment by Amazon (FBA) fee adjustments, and an exciting new selection program for our European marketplaces. Our costs have increased significantly this year, primarily due to our largest ever one-year investment in Free One-Day Delivery in FBA. Nevertheless, we will make only limited increases in our fulfillment fees as we identify opportunities to leverage our scale for further efficiencies.
Please review the fee change help pages below. The changes will take effect April 1, 2020, except where otherwise stated, and will be applicable in our European marketplaces.