China and the United States spend a considerable amount on their militaries on average. Most other G20 countries spend relatively less - try zooming in to get a better look.
Interestingly, Saudi Arabia, despite having nearly half the average GDP per capita, spends about as much on military spending per capita as the United States does on average. See the below charts for more information on Saudi Arabia's spending.
Countries like Australia and Canada are roughly as populous as Saudi Arabia, but do not spend nearly as much of their GDP on the military as the Saudi Arabian's do, maxing out at spending 13.33% of their GDP on the military in 2015.
The sharp downturn in spending for Saudi Arabia in 2016 came as an effect of low oil prices during this time , leaving the country in a significant deficit from the previous year.
Saudi Arabia spent nearly double what it did on military expenses per capita as it did on healthcare per capita between 2010 and 2017.