Ancestry.com has two indexes for deaths in Cook County:
Ancestry.com. Cook County, Illinois Death Index, 1908-1988 [database on-line]. Provo, UT, USA: Ancestry.com Operations Inc, 2008. Original data: Cook County Clerk. Cook County Clerk Genealogy Records. Cook County Clerk’s Office, Chicago, IL: Cook County Clerk, 2008.
Ancestry.com. Cook County, Illinois, Deaths Index, 1878-1922 [database on-line]. Provo, UT, USA: Ancestry.com Operations, Inc., 2011. Original data: Illinois, Cook County Deaths 1878–1922.” Index. FamilySearch, Salt Lake City, Utah, 2010. Illinois Department of Public Health. “Birth and Death Records, 1916–present." Division of Vital Records, Springfield, Illinois.
Are these indexes based on the same ingestion of the records, or can they be considered somewhat independent? The reason I am asking is that I am looking for a death record for Samuel M. Rothschild, whose death is reported here in the Chicago Tribune on 7 Jan 1920:
If the two collections are based on the same scan of the data, then the omission of the same record from both collections is not an independent event, probabilistically-speaking. If, however, the two scans are independent, it seems much less likely that they both accidentally skipped the same record. Then the possibilities are that he did not die in Cook County, or that his death was not reported. His death is not recorded in the Illinois State death index either, and his death notice does not mention him dying away from home, so I am at a bit of a loss to account for the details of his death.
What other hypotheses should I entertain? Where else might he have died? For the record, he sometimes went by the name Marcus, and was born in 1835 in Germany, probably in Hesse-Darmstadt.