Bmi Female Age 2 Math Equation Needed!?

Math Equation Needed!? - bmi female age 2

Well, that's the problem. This is the index of average body mass of women in the United States in 2000.

Age BMI
2 16.4
3 15.7
4 15.3
5 15.2
6 15.21
7 15.4
8 15.8
9 16.3
10 16.8
11 17.5
12 18.18
13 18.7
14 19.36
15 19.88
16 20.4
17 20.85
18 21.22
19 21.6
20 21.65

Basically, if this table, it looks like a later "S". But here is my question.

What type of model behavior chart? Explain why you chose this function. Create a formula (model) that fits the graph.

If you could help me, an equation, and what kind of function that ... I would be eternally grateful!