An Abundance of Nicknames

There are a few girls' that have arguably remained popular because of the wide variety of nicknames (or have they gotten so many nicknames because they're so popular? Hmmm...chicken or egg...). You can kind of guess the age of someone with one of those names based on which nickname she uses--Ellie is probably a small child, but Betty? She's the grandma.
It occurred to me that since there will always be a percentage of parents who prefer to just use the nickname as a full name, you could probably track when each diminutive was most popular simply with the SSA data.
So, that's what I did, for three classic, nickname-abundant girls' names. Some of the nicknames are now considered full names in their own rights, but I still threw them in because it's interesting.

First up is Margaret (the x-axis is year, obviously; the y-axis is % of girls born that year):

With the exception of Megan for a couple decades, Margaret has remained more popular than any of its nicknames or variants alone. However, it's pretty hard to see how the less-common forms have moved around! So here are the top 5 forms (minus Margaret herself):

And here're only the more "nicknamey" forms (that is, the ones generally not thought of as 'full names'):

Next up is Katherine. More than either of the others, Katherine probably has the most spelling variants, both for itself and its nicknames. However, I only used the most popular spelling for each form.

Whoa, Karen got really popular! So did Kathy! Again, the top 5 forms, excluding Katherine herself:

I'm actually surprised Katie is still so close to Kate in popularity. It seems so '80s to me.
Here are only the more "nicknamey" forms:

Kathy had quite the peak, didn't it? And Kate is now the most common nickname form, and second most common, after Katherine. 

Oh, deep breath. Here's comes the big one. Elizabeth. 

That's a lot of data. I'll think I'll break this one up into a few charts. 

Here are the top 5 forms overall, minus Elizabeth:

These are the top five "nicknamey" forms:

And the bottom 5:

Aw, poor Libby. Way down there where you can barely see her. 

And finally, just for fun, really, here are the less-common "full-name" forms:

Now, I'm guessing that my hypothesis doesn't always work out: for names less connected to their full forms (in English, anyway), the charts probably don't accurately reflect their usage as nicknames in the US--Kaia and Megan for example. But for the really "nicknamey" forms, I bet it comes pretty close. ;)