Problems with Cook County,Illinois Death Index, 1908-1988?

Richard Carruthers wrote to AskOliveTree.blogspot.com with a very informative and interesting study he has undertaken.

Because Richard's email is quite long I have edited it for publication here on OliveTreeGenealogy.blogspot.com. It will be useful for thos searching in Cook County Illinois Death Records on Ancestry.com

In 1886, Edmond Henry ROBERTS) married Illinois-native, Minnie C.
SMITH. They had four daughters and one son all born in Illinois between 1887 and 1903. I have located all but the youngest daughter in on-line Cook County birth indexes on the new LDS prototype page.

I checked the "Cook County,Illinois Death Index, 1908-1988" which is online at Ancestry.comand found no relevant entries. I have tried
several ways to search for them, and have had some very curious results about which I thought you might like to know and consider.

First, in the search box provided by ancestry.com, I put in the surname ROBERTS. That yielded a total of 2,058 results for the entire span of the collection, but no Edmond/Edmund ROBERTS entries at all. There were 5 records for a Minnie ROBERTS, but the likeliest who died in 1943 when our Minnie (SMITH) ROBERTS would have been about 75 years old, turned out to be for a Minnie Spencer ROBERTS

Then I looked more carefully through my old files, and found that years ago (on 30 May 2000!), I had copied from LDS microfiche number 6016533, records from the actual index produced by Cook county, which covers much of Chicago. Labelled "Cook County Illinois Bureau of Vital Statistics 1877-1916", and had found the following entries which looked promising:

on MFC 53/70 (all bearing the number 6016533)

Name Date of Death Age Place Certificate Number
ROBERTS, Edmund H.; Dec 14 1911; 50 YR; Chicago; 0000016378
ROBERTS, Minnie; Feb 7 1911; ?40 YR; Chicago; 0000016096
ROBERTS, Minnie; Dec 3 1915; 30; Chicago; 0000017450

Armed with this information, I returned to the ancestry.com database 1908-1988 decided to leave all fields except the one for the year blank in the search box. It turned out that no death records are indexed for anyone dying in Cook county, Illinois in 1911 appear in the index. Then I tried a bunch of other years, and finally did a systematic search of records using only the year in the box provided
for that. The results that yielded were very interesting and rather disappointing.

First off, the database actually contains death records starting as early as 1897, but missing for 1910, 1911, 1912, 1913, and 1914 entirely. For the rest of the years to 1916 I got the following results:

1897-1 record
1898-10,858 records
1899-8,513 records
1900-14,040 records
1901-7,964 records
1902-5,872 records
1903-4,903 records
1904-3,393 records
1905-2,335 records
1906-4,234 records
1907-6,487 records
1908-14,918 records
1909-287 records
1910-1914 no records at all!
1915-35,402 records
1916-39,673 records

These are records for a database that supposedly covers the period 1908-1988 and contains 2.7 million records according to ancestry.com's own on-line information!

Examining the entries over the foregoing period, I discovered that from 1897-1915 all the records appear to cover only names where the first name is made up of two letters and the last name is made of four letters! Most of these names appear to be entirely nonsensical. I suppose that some of them may include the deceased person's initial and the first four letters of their surname, but this is by no means clear. There is no explanation of this shortcoming in the explanatory information that ancestry.com provides about this database. It is surely relevant, too, that only in 1916 do real names as we use them appear in the index. At least I can report that this happens most of the time. Some records still appear in the 2-4 letter format of the earlier years.

Clearly there are problems with this database. I know from the microfiche that the real records indexed by Cook County, Illinois's Bureau of Vital Statistics exist for the period 1871-1916 in an entirely comprehensible, standard format. What then is the online database purporting to cover the period 1908-1988? For one thing, it
doesn't cover all the years from 1908 to 1988 as advertised, and in fact contains records from at least a decade earlier. The coverage, however, only appears to begin to be accurate from 1916, though it still has some of the problem material over the earlier years I've already outlined. It's really misleading to a researcher not to be
alerted to these deficiencies in the ancestry.com version of the index.