The "Disparity Index" measures the likelihood drivers of a given race or ethnic group are stopped based on their proportion of the residential population age 16 and over.
You know, the more I think about this the less plausible it sounds.
Why would the residential population be the baseline? Wouldn't the relevant metric be the proportion of drivers on the roads?
I have no idea what the Ferguson area is like, so what is the racial makeup of the surrounding towns? If they are mostly white then you'd expect drivers in Ferguson to be white in a higher proportion than the population of Ferguson. If they are mostly black then you'd expect drivers in Ferguson more likely to be black than the population of Ferguson, and thus blacks would be more likely to be pulled over without any racial discrimination occurring.
After all, drivers don't just drive in the town they live in. Particularly in tightly-packed small suburbs in a metropolitan area a driver likely drives through many towns during their daily commute.
So, I don't think this statistic is really relevant without knowing more information than is available so far.
eta: one other possibility is age demographics. If the whites are on average 60 years old and blacks are on average 30 years old (I'm talking about drivers here) then blacks are more likely to get stopped more simply because younger drivers are more reckless, prone to speeding, etc. And given how quickly Ferguson's race demographics has changed in the last 20 years such a large disparity wouldn't surprise me at all, as younger people are more likely to move frequently while older people tend to stay put.
Why is it so implausible? Ferguson PD managed to wrongfully arrest journalists covering the protests, and do so with lots of evidence showing that. If they are arrogant/stupid enough to do that, why is racial profiling hard to believe?
The number of drivers on the road
would be better -
if there was any way of calculating it. There is anecdotal evidence that blacks from neighbouring areas avoid Ferguson due to a fear of racial profiling. This might suggest that the black driving population would be smaller than their driving-age representation would suggest.
I can accept an argument that this might cause uncertainty in the numbers, but there is no reason to expect any error to falsely reflect badly on Ferguson PD.
You have raised a possible (and probably small) source of error, which could go either way, and on that basis rejected the numbers - which are fairly large. This is a force of 53 officers who stopped more than 88 black drivers a week and 13 white drivers a week.
Also such a hypothetical source of error can explain neither the search rate nor the contraband hit rate differences. Nor can it explain why, when they are arrested, whites are more likely to be arrested for unequivocal offenses whilst for blacks,
'Officers rely heavily on the municipal “Failure to Comply” charge, which appears to be facially unconstitutional in part, and is frequently abused in practice. FPD also relies on a system of officer-generated arrest orders called “wanteds” that circumvents the warrant system and poses a significant risk of abuse. The data show, moreover, that FPD misconduct in the area of stops and arrests disproportionately impacts African Americans.'
The report then gives examples.
If you were black, would you trust a police force where the second-ranking officer was blatant enough in his racism to be sending racist emails?
The report criticizes the lack of paperwork for detentions, but still manages to find unconstitutional arrests that have been documented by the officers. There is every reason to suspect that others have been missed.
'13 FPD policy states that “[o]fficers should document” all field contacts and field interrogation “relevant to criminal activity and identification of criminal suspects on the appropriate Department approved computer entry forms.” FPD General Order 407.00. Policy requires that a “Field Investigation Report” be completed for persons and vehicles “in all instances when an officer feels” that the subject “may be in the area for a questionable or suspicious purpose.” FPD General Order 422.01. In practice, however, FPD officers do not reliably document field contacts, particularly of pedestrians, and the department does not evaluate such field contacts.'
'As with its pattern of unconstitutional stops, FPD routinely makes arrests without probable cause. Frequently, officers arrest people for conduct that plainly does not meet the elements of the cited offense. For example, in November 2013, an officer approached five African-American young people listening to music in a car. Claiming to have smelled marijuana, the officer placed them under arrest for disorderly conduct based on their “gathering in a group for the purposes of committing illegal activity.” The young people were detained and charged—some taken to jail, others delivered to their parents—despite the officer finding no marijuana, even after conducting an inventory search of the car. Similarly, in February 2012, an officer wrote an arrest notification ticket for Peace Disturbance for “loud music” coming from a car. The arrest ticket appears unlawful as the officer did not assert, and there is no other indication, that a third party was disturbed by the music—an element of the offense. See Ferguson Mun. Code § 29-82 (prohibiting certain conduct that “unreasonably and knowingly disturbs or alarms another person or persons”). Nonetheless, a supervisor approved it. These warrantless arrests violated the Fourth Amendment because they were not based on probable cause. See Virginia v. Moore, 553 U.S. 164, 173 (2008).'