what is the average number of gold medals won by the top 5 nations?
2.6
col : rank | nation | gold | silver | bronze | total row 1 : 1 | united states | 5 | 6 | 5 | 16 row 2 : 2 | jamaica | 4 | 1 | 1 | 6 row 3 : 3 | netherlands | 2 | 0 | 0 | 2 row 4 : 4 | bahamas | 1 | 1 | 0 | 2 row 5 : 5 | ukraine | 1 | 0 | 1 | 2 row 6 : 6 | east germany | 1 | 0 | 0 | 1 row 7 :  | greece | 1 | 0 | 0 | 1 row 8 :  | soviet union | 1 | 0 | 0 | 1 row 9 : 9 | ivory coast | 0 | 2 | 0 | 2 row 10 :  | united kingdom | 0 | 2 | 0 | 2 row 11 : 11 | belgium | 0 | 1 | 1 | 2 row 12 : 12 | bulgaria | 0 | 1 | 0 | 1 row 13 :  | russia | 0 | 1 | 0 | 1 row 14 :  | germany | 0 | 1 | 0 | 1 row 15 : 15 | canada | 0 | 0 | 2 | 2 row 16 :  | france | 0 | 0 | 2 | 2 row 17 : 17 | belarus | 0 | 0 | 1 | 1 row 18 :  | cuba | 0 | 0 | 1 | 1 row 19 :  | gabon | 0 | 0 | 1 | 1 row 20 :  | british virgin islands | 0 | 0 | 1 | 1 row 21 : total | total | 16 | 16 | 16 | 48
what is the average number of gold medals won by the top 5 nations?
Rank Nation Gold Silver Bronze Total
1 United States 5 6 5 16
2 Jamaica 4 1 1 6
3 Netherlands 2 0 0 2
4 Bahamas 1 1 0 2
5 Ukraine 1 0 1 2
6 East Germany 1 0 0 1
Greece 1 0 0 1
Soviet Union 1 0 0 1
9 Ivory Coast 0 2 0 2
United Kingdom 0 2 0 2
11 Belgium 0 1 1 2
12 Bulgaria 0 1 0 1
Russia 0 1 0 1
Germany 0 1 0 1
15 Canada 0 0 2 2
France 0 0 2 2
17 Belarus 0 0 1 1
Cuba 0 0 1 1
Gabon 0 0 1 1
British Virgin Islands 0 0 1 1
Total Total 16 16 16 48
2.6