I just came across this, from 1999:

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http://www.bmj.com/cgi/content/full/319/7225/1615

The much maligned "Sharon", "Tracey" and "Sandra", who have been the butt of so many Essex girl jokes, are finally vindicated in this week's Christmas issue of the BMJ as researchers find that the real culprits of easy virtue are "Kelly" and "Louise".

In an analysis of 16-24 year old females attending a genitourinary clinic in Southampton, Dr Elizabeth Foley and colleagues found that contrary to popular belief, Sharon and Tracey were not the most popular names of attendees. They actually found that of the 1462 women who attended the clinic the top ten names most frequently seen were:-

1. Sarah
2. Emma
3. Kelly
4. Louise
5. Claire
6. Lisa
7. Rachel
8. Clare
9. Michelle
10. Nicola

The authors are quick to point out that they compared these findings with data from the Office of Populations Censuses and Surveys and they found that most of the top 10 names for women attending the department were seen with the frequency expected by the incidence of the name in the population. Nevertheless, some names were more popular among the study group at the clinic than they were in the general population, including Kelly, Louise and Clare (with no "i").

The much maligned Sharon, Tracey and Sandra, however, were seen half as often as expected and the authors say that as we enter the new millennium these names should make way for the more popular "Hampshire Girls".
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Now, it seemed to me that these frequencies ought to correlate with the frequency of occurence of names in song. But I can only think of songs or tunes featuring about half of those names, and none for a Kelly or Clare. And 200 years ago would the pox wards have been full of Janets and Nancys?