In reality, what Chomsky compared was the amount of coverage of the murder of Popieluszko with the amount of coverage given to the murders of one hundred Latin American clerics. Tables of data in Herman and Chomsky's book Manufacturing Consent reveal dozens of different skewed ratios, each showing that the US press seemed to regard the murder of a Latin American cleric as less than one percent as important than the murder of a Polish cleric. According to Chomsky, this paired-example is evidence supporting his claim that the US press functions as a poweful government-supporting propaganda machine.
Lehrer also omits all the ratios, and never reveals what was the primary measure the authors of Manufacturing Consent used for estimating the amount of press coverage. What Herman and Chomsky did was simply compare the number of column-inches of article-descriptions about each of these subjects that are in yearly indexes of New York Times articles.
This is a very simple way of estimating the amount of news coverage given by the US press, which can be easily duplicated by anyone with access to a large main library of a US university.