For me this will be the deciding factor on how many children we have (and also max age I want to be...but that can always be stretched). Now I use to think the best gap was two years...that is what is between me and my sister and that is what most people I know say is there "perfect" age gap. But is two years really the perfect age gap? Or has that just become the norm? Is the age gap getting larger over the years? I know a couple people who want large age gaps (to me that is over 5 years) or others that is just the way it worked out for their family. But if you had to choose and had total control (which is very unlikely but lets just go with it :D) over the age gap between your kids what would it be???
I found this article at THE TIMES it points to a three year age gap but states that what ever the age gap you have to make sure that you prepare the older child for a sibling. Also to make sure that you make each child feel special in their own way. But if you go here (to the writer's blog) you can see Sarah Ebner's full article including the missing case study.
Another one BabyCentre talks about the increase of premature birth rates are higher if become pregnant before 6 months and above 5 years. Also points out that with a smaller gap the expenses are closer together but you get the baby part over quicker. While with a larger gap expenses are over a larger time frame and you may feel like you can focus on each child more.
Below is my personal thoughts on choosing an age gap.
I personally wouldn't mind having two in diapers...I use cloth diapers so for me this would not be a major cost. I currently have all the newborn diapers that I would last through at least 2 if not 3 more children.
I really want to have a baby either before my older is being potty trained or has been potty trained for awhile. I have heard several hundred times of moms who said that they were some what potty trained and then regressed when baby came along. I think this is harder to pin point as every child potty trains at their own time.
Never get out of baby mode.
This can be a positive or a negative. One way you won't feel like you are starting all over again like you might if you wait 4+ years. On the other hand it feels like you always have a baby tied to your hip...you may feel like you don't get to enjoy the older child and their growing independence.
On maternity leave with your friends.
This seems like a very trivial way to base the age gap on but it can/could be important to some. So you want a friend to be off at the same time or go through pregnancy together. My sister-in-law was pregnant the same time as me and it was very fun! Especially if you are due as close as we were (my daughter born three days after my niece). We got to complain about morning sickness and heartburn together. It felt like you had someone who truly understood what you were going through...because they were!
Having children closer means that you pay a larger amount at one time (or closer together). If they are farther apart there is breathing room to add to the savings. But this also means that you will be paying for University of a larger span which can be hard if you want to save up for retirement. With a smaller gap you can start on retirement savings sooner.
But I guess when it comes down to it as long as we give the same attention (as possible) to each child I think any age gap can work out. There are positives and negatives to any age gap. Also I think a small age gap is just as likely to give you close children as a larger age gap. Though I still think I would love a two year age gap...that is if everything goes as planned. :D
Lots of Bunny-Hugs!
p.s. if you google "perfect age between kids" there are a lot of blogs, articles, and forums that bring up this topic.