If we include countries which have a population under 1 million:
#1 Tuvalu: 19073.57
#2 Monaco: 16448.48
#3 Nauru: 10702.05
#4 San Marino: 10225.01
#5 Liechtenstein: 5770.17
#6 Palau: 5677.40
#7 Anguilla: 5371.64
#8 Estonia: 2468.62
#9 Seychelles: 2403.67
#10 Iceland: 2378.70