How feet grow: a selection of abstracts

So I thought I was going to get to see a little tacker with a 2-size difference in foot length. Turns out they saw someone else, but in the process I came across these few interesting articles:

Foot Growth in Children Age One to Five Years

Foot & Ankle International February 1990 vol. 10 no. 4 211-213 by Gould et al.

The Lowdown: 

Kids feet grew: 1/2 a size in less than 2 months up till 15 months old

1/2 size in 2-3 months from 15-24 months

1/2 size every 3-4 months from 2-3 years

1/2 size every 4 months from 3-5 years

Boys feet were on average 1 size longer and wider than girls. Width and length growth were proportional.

Next:

Foot Growth Rate in Children Age One to Six Years*

Foot & Ankle International January 1983 vol. 3 no. 4 207-210  By Wenger et al.

They used to think shoe size changed every 1-2 months from 2-6 years:

Their study showed a size change (I assume a half size?) every 2-3 months from 12-30 months then 4 months 30-48 months then 6 months 4-6 years.