The original source[1] of the news article provides a lot more detail and information. Interesting that a British passport has climbed up in the ranking two places to 4th place, despite Brexit, while the US passport is declining.
The company also has a useful database of all passports you can check for your own passports and see what countries you can enter visa-free.[2]
The company also has a useful database of all passports you can check for your own passports and see what countries you can enter visa-free.[2]