CR - Pickpockets - Answer Key

The correct answer is D.

We're asked to explain the "surprising trends" (plural) in the frequency of reported incidents of pickpocketing at New City's main train station. There are two trends, both statistically related to the presence of temporary signs warning passengers to beware of pickpockets: 

  • When the signs were erected, the reported incidence of pickpocketing tripled immediately.
  • As soon as the signs were removed, the rate returned to its original level, just as quickly.

It's possible that the two trends could have happened for entirely different reasons. However, given that (i) the elevated rate of reported pickpocketing coincided exactly with the presence of signs and (ii) the rate returned to exactly its original level once the signs were gone, we can safely dismiss this possibility. (Correct answers will not depend on extraordinarily improbably choices.)

So, we need some circumstance, simultaneous with the presence of the signs, that can reasonably explain why there were three times the usual number of reports of pickpocketing, per passenger, during that period only.

A correct answer could do either of two things: 

  • It could give a reason why passengers were 3 times as likely to actually be pickpocketed while the signs were posted;
  • It could give a reason why passengers were 3 times as likely to reporthaving been pickpocketed during that period.

Use these as standards by which to judge the answer choices.

This statement would be relevant only if a drastically different proportion of passengers traveled at peak hours during the period when the signs were posted. No such change is described or implied, so this choice is irrelevant.

This choice means, essentially, that pickpocketing victims have no economic motivation to file a report. 
If victims could recover (at least some of) their losses as a result of reporting the theft -- whether from the thief, if she/he were caught, or by submitting the report to an insurer -- then the signs might, by reminding the victims of this, encourage more such reports. If victims have no reasonable chance of being reimbursed, though, then that eliminates this consideration (which is already very weak) as a possible explanation.

Switching from cash to electronic fare cards would, if anything, decrease the frequency of pickpocketing -- simply because passengers would no longer have to carry cash in an immediately-accessible place. Therefore, if this statement is true, we would expect a gradual decline in pickpocketing throughout the transition period, as fewer and fewer passengers would pay with cash -- and we would expect the theft rate to settle at a level lower than its pre-transition value. So, this statement does not adequately explain either trend. (Even if the use of fare cards somehow made pickpocketing more likely -- already an implausible suggestion -- neither the drop in thefts nor the abruptness of either change would be any easier to understand.)

If this statement is true, then, as they passed through very specific areas of the station (= near the signs), a large proportion of passengers would inadvertently indicate the exact location of their valuables to anyone who might be watching. It's possible, of course, that this "spot checking" could have made the passengers themselves more alert, too -- but those who had to stop and put down their luggage could not possibly have maintained the same degree of vigilance once in motion again. Thus, according to this choice, the signs ultimately made pickpockets both more accurate and more efficient.

The passenger quotes crime rates per passenger using the station, so the absolute number of passengers is irrelevant. Even if increased crowding led to a disproportionate increase in pickpocketing -- a reasonable supposition, which would cause per-passenger theft rates to increase -- this choice does nothing to explain why the theft rate dropped after a certain period. Nor does it explain the abruptness of either change.