Walking speed depends on size of city where you live. As bigger city, as faster you will walk.
According to research conducted in 31 cities across the world, fastest speed of walk in Singapore (6.15 km per hour), Copenhagen (6.5 km per hour), Madrid (6.5 km per hour), Guangzhou (6 km per hour) and Dublin (6 km per hour). Speed of walk increasing because of hectic lifestyle. Distance between places increasing every year (because of cities expansion) but we still have same 24 hours. Increased speed of walk create illusion of less time spend on commuting.
Correlation between walking speed and city population proved. As cities grow larger cost of living also increase. This influence of humans behavior and stimulate to walk faster in order to have more resources.