the age of completing potty training I have noticed is a lot older. Mine were at 18 and 20 months but I have friends who's children are 3 and 4 and still not potty trained.

I blame the advances in diaper technology. Frankly, diapers are so good at keeping bumbs dry the tots don't know what it's like to be uncomfortable. Hence they have no urge to bother with potty training.

I raised my kids with cloth diapers. I bet they hated being wet and that encouraged them to control themselves at such a young age, Personally, I think it disgusting that a 3, 4, or even 5 year old still wear a diaper/pull-up. Look, if your child is old enough to tell you they are wet or have dirtied themself they are old enough to have learned not to.