In January Open Data Watch updated their Open Data Inventory to reflect changes in 2016. The inventory "assesses the coverage and openness of official statistics" for nearly every country across the globe.
You can view a ranked list of countries here with scores broken down into categories focused on coverage of official statistics and their openness. In 2016 In 2016, Sweden took the top spot. The Czech Republic, Norway, Poland, Lithuania, Denmark, Estonia, Canada, the United States and Finland round out the top 10. Read the full report here.