In March of 1978, Brink's Inc. was awarded the contract to collect coins from approximately 70,000 parking meters in the city of New York. In response to an anonymous tip that not all money collected by Brink's was being delivered to the city's finance depository, the city began an investigation of parking meter collections. Through the use of "salted" coins (coins treated with a fluorescent substance and inserted into specific meters) and surveillance cameras, five Brink's employees were arrested and subsequently convicted of grand larceny and criminal possession of stolen property. When they were arrested, they had in their possession $4,500 in coins stolen that day from parking meter collections. (For a complete background and references see De Groot et al. (1986), Statistics and the Law, John Wiley & Sons, New York).
As a result, a civil suit was filed by the City of New York alleging that Brink's had failed to honor its contract and acted negligently. The city was seeking monetary compensation from Brink's for losses incurred by the criminal activities of its employees. Brink's was subsequently found guilty of negligence and breach of contract. The question remained as to what the actual dollar amount of the damages were. Although the exact calculation of monetary loss is impossible to determine, the law allows for the introduction of testimony regarding the estimation of such loss as a ``...matter of just and reasonable inference.''
Brink's' contract was terminated in March of 1980 and a new contract was awarded to CDC, Inc. in June of 1980. A dataset covering both the Brink's and the CDC's collection periods is given in the following Table, where M=month, Y=year, NCOL1A=# of collections including area 1A, TINCOME1A=total income including area 1A, AINC1A=average income including area 1A, INC1A=income of area 1A, AI1A=average income of area 1A, N1A=# of collections in area 1A. Area 1A was a small area around the city hall where the collection was done by city employees throughout this time period.
William Fairley was hired to help the city's attorneys determine the amount of money which Brink's had failed to collect over the entire term of their contract (May '78 to Mar '80). Fairley noted that the first ten months of collection by CDC exceeded all ten month periods collected by Brink's by $1,000,000. He decided to compare the last ten months of Brink's (Jun '79 to Mar '80) to the first ten months of CDC (Jun '80 to Mar '81). He and the city's attorneys reasoned that this was reasonable since the introduction of very strict oversight during the CDC period assured the absence of theft. However, he noted that the increase in revenue during the CDC period may have been the result of an ongoing trend (i.e., if Brink's' contract had not been terminated they too would have experienced an increase in revenue), or, the increase in revenue could have been attributed to a seasonality effect (i.e., the months which exhibited an increase may have occurred during months which exhibit higher than average revenue collection), or to some other specific cause.
Bruce Levin, the expert witness for Brink's, attacked the City's case on two issues. First, he argued that there exists an upward trend throughout the Brink's period, followed by a ``leveling'' off during the CDC period, which implied that a constant trend through the Brink's period is clearly not representative of the actual trend; and second he argued that the difference between the two periods may be attributable to factors other than theft. He presented evidence of a gasoline shortage that led to ``marked drops'' in revenues for automobile toll bridges and tunnels. This happened during the Brink's period, June-September 1979.
The following program allows you to plot in various ways this dataset.
For a complete analysis of this dataset see the paper by Bentow and Afshartous.