I've been reading other blog entries on this index at the Cook County Illinois County Clerk's Office. So far I have not seen comments about what is in the database.
There is nowhere on the site that I could find where one could see what years were in the database. My search for the last name of Jones in the years 1910 to 1915 resulted in only the handful of hits shown here. This seems a little on the low side to me.
A search of Smith birth from 1915 to 1920 yielded over 1000 entries. A search of Smith from 1910 to 1915 yielded less than 20.
I'm appreciative of having the index online for free, but am frustrated with being unable to find out just what is in the index. Comments to this are welcome.