Episode premiere: 7 November 2026 at 7:30 am IST. Read the full case study before the premiere.
A claim that violence fell by 70%
October 2016. A public meeting of New York City's jail oversight board. A senior jail official brings good news about a new kind of housing unit on Rikers Island. Violence there, he says, is "down by over seventy percent". Those units were designed with help from one of the most famous consulting firms in the world: McKinsey and Company.
Three years later, an investigation would ask a simple question. Were those numbers real? This is the story of Rikers.
The client
Rikers Island is a four-hundred-acre island in New York City. It holds the city's main jail complex. The client was the city's Department of Correction. Its business model is simple to describe. It has no customers and no profit. It is paid for by taxpayers. In 2015, it had a budget of about eight hundred and sixty million dollars a year, around nine thousand officers, and about ten thousand people in custody on an average day.
And it had a problem. According to ProPublica, in the two years before 2014, the most serious violence between inmates, and the use of force by guards, had both jumped more than fifty per cent.
The hire
In 2014, New York had a new mayor, Bill de Blasio, and a new correction commissioner, Joseph Ponte. That September, the department hired McKinsey, on a contract worth one point eight million dollars, to find the causes of the violence and propose solutions. Three current and former correction officials told ProPublica that the mayor's aides saw hiring McKinsey as a way to head off the need for a federal jail monitor, and as political cover.
The mayor's office denied it. In October 2015, a federal court approved a settlement in a case called Nunez versus the City of New York. A federal monitor was appointed anyway.
The plan
In March 2015, the city announced a fourteen-point anti-violence plan, worked out with McKinsey. One part of it was a new kind of housing unit, called Restart. By July, eight Restart units, holding about two hundred and fifty people, were open in one jail on the island, the George Motchan Detention Center. They were also a testing ground for McKinsey's main tool: an algorithm called the Housing Unit Balancer, or HUB.
HUB was meant to predict how likely each person was to be violent, and then spread people across housing units to lower the risk. The early results looked remarkable. ProPublica reported a single violent incident in the first few months, compared with thirty two in units without the new approach.
The selection
ProPublica reported a problem in how the first units were filled. According to the investigation, jail officials replaced some people selected by HUB, who were considered troublesome, with alternates believed to be more accommodating, chosen from a list provided by McKinsey. McKinsey acknowledged to ProPublica that potentially unruly inmates were intentionally excluded from the earliest Restart units. Asked about it in a deposition, Commissioner Ponte said: “We did that, so that wasn’t news.”
Ponte and McKinsey said the filtering later stopped. Seven current and former senior correction officials told ProPublica that it continued after McKinsey handed the selection process to the department. If that account is right, the early comparison may have measured who was placed in the units as much as the effect of the method itself.
Source context: [1]
The numbers
There were also doubts about the data itself. According to City Hall, coding errors had inflated the starting level of violence by ten to fifteen per cent, making later drops look bigger. In 2017, according to emails reported by the New York Daily News, at least five department staff raised concerns about McKinsey's figures. In June 2017, one project specialist wrote: "Validity of currently reported data is questionable."
That same month, the department's chief of staff signed off on a payment to McKinsey of nine hundred and seventy three thousand, nine hundred and forty one dollars. And the federal monitor had already noted that the Restart jails accounted for the largest amount of missing documentation.
Design a pilot that is allowed to fail
- 01Fix the selection rule
Decide in advance who enters the pilot and comparison groups, and log every exception.
- 02Validate the baseline
Audit how incidents are counted before and after, and test whether coding changes move the numbers.
- 03Hear the data owners
Give staff who record the data a route to challenge results before they are announced.
Follow the money
Follow the money. The first contract, in September 2014, was worth $1.8 million. By the spring of 2015, McKinsey had been paid more than $6 million, and in November 2015 the city agreed to $7.5 million more. By the time the work ended in April 2017, the total had reached $27.5 million, of which about $5.5 million was for data analytics, according to ProPublica.
Part of that work was IntelWatch, a tool designed, according to ProPublica, to predict gang affiliation and future violence by mapping inmates’ networks from phone calls, visitors and commissary deposits. McKinsey’s slides used names of characters from the film Gangs of New York as stand-ins for real inmates. ProPublica reported that the tool was finished in a rush, riddled with bugs, and paid for but never used.
The reckoning
ProPublica compared 2019 with 2014 using the city’s own data: inmate attacks on other inmates were up 25%, assaults on staff up 15% and use of force by guards up 25%. Using the metrics McKinsey employed, it reported that violence had risen nearly 50% since the firm began its assignment. These are outcome measures for a whole jail system over a period of many changes; they do not isolate the effect of any one programme.
In March 2017, Mayor de Blasio announced that he intended to close Rikers. About a year later, the George Motchan Detention Center, home of the first Restart units, became the first jail on the island to shut, and the department abandoned Restart. In October 2019, the City Council voted 36 to 13 for an $8.7 billion plan to replace Rikers with four smaller borough jails.
The other side
It is important to be fair. McKinsey said the Restart units experienced substantial reductions in violence, measured against comparable groups of inmates. It denied that its consultants were involved in any effort to improperly skew or reduce the reported levels of violence. City Hall said the consultants were not involved in final housing decisions. The department said: "We stand by the reduced rates of violence we saw in our Restart units."
And the city planned to keep some of the work, including HUB, for the jails that will replace Rikers. But the federal monitor kept reporting. In 2020, his report found that the rate at which officers used force was higher than in any previous monitoring period.
THE SEQUENCE
A timeline of the case
McKinsey is hired
A $1.8m contract to find the causes of violence and propose solutions. [1]
A fourteen-point plan
The city announces an anti-violence plan developed with McKinsey. [3]
Restart units open
Eight units holding about 250 people operate at GMDC. [1]
Federal consent judgment
Nunez v. City of New York brings a federal monitor. [4]
A 70% claim
An official tells the oversight board violence in the units is down by over 70%. [2]
Work ends at $27.5m
McKinsey’s engagement concludes after successive increases. [1]
Investigation published
ProPublica reports selection, data and outcome concerns; McKinsey and the city dispute them. [1]
Monitor’s tenth report
Use of force per person is higher than in any previous monitoring period. [4]
A pilot is a measurement instrument
Most organisations treat a pilot as a first step in delivery. In practice, a pilot is also an experiment, and its results will be used to make decisions about scale, budget and reputation. That means its design determines what the results can show. If the people entering the pilot are chosen differently from the people outside it, a better outcome may reflect who was selected rather than what the programme did.
ProPublica’s reporting on the early Restart units turns on exactly that point. According to the investigation, people selected by the HUB model and considered troublesome were replaced with alternates believed to be more accommodating, and McKinsey acknowledged that potentially unruly inmates were intentionally excluded from the earliest units. McKinsey and the former commissioner said the filtering later stopped; seven officials told ProPublica it continued. Whichever account is closer to the truth for the later units, the early comparison could not cleanly measure the method.
Fix the selection rule before the results arrive
The practical safeguard is to write the selection rule down before the pilot starts and to log every exception. If the rule says participants will be allocated by a model, any manual substitution should be recorded with a reason and an approver. If exclusions are necessary for safety, the comparison group should be adjusted in the same way, or the analysis should say plainly that the groups differ.
This is not a technical nicety. Once a striking number such as “down by over 70%” is presented publicly, it becomes difficult to revisit. Officials, advisers and the media begin to treat it as a fact about the programme. A selection log is the evidence that allows a later reviewer to check whether that number was comparing like with like. The Allstate claims case offers a different example of how internal documents later become the record against which public claims are tested.
Baselines can move the result as much as the programme
City Hall’s acknowledgement, as reported by ProPublica, that coding errors had inflated the starting level of violence by 10% to 15% shows a second risk. A pilot’s improvement is measured against a baseline. If the baseline is overstated, the improvement looks larger than it is. Changes in how incidents are classified, who records them and which records are missing can all shift the numbers without any change in behaviour on the housing units.
The federal monitor’s observation that the Restart facilities accounted for the largest amount of missing documentation, as reported by the New York Daily News, belongs in the same category. Missing records do not prove that results were manipulated. They do mean the results cannot be fully verified. A pilot dashboard should show data completeness alongside the outcome measure, so that a decision-maker can see whether a rise or fall is supported by complete records.
People closest to the data see problems first
The reported internal emails, including the June 2017 note that the validity of currently reported data was questionable, are a familiar pattern. The staff who record incidents, reconcile spreadsheets and answer follow-up questions often notice inconsistencies before leaders do. When several of them raise concerns, that is a signal worth pausing for, even if their concerns later prove resolvable.
A good engagement creates a route for that signal. The route should be known to the client’s staff and the consultants, should not depend on the people who will present the results and should produce a written response. The response may confirm the data, correct it or qualify the claim. Any of those outcomes is better than an unrecorded concern. The Enron case is a reminder that organisations can reward confident narratives while discouraging the people who question them.
Be clear about why the adviser is there
ProPublica reported that three officials believed mayoral aides saw hiring McKinsey as a way to head off a federal monitor and as political cover; the mayor’s office denied it. The claim is contested, and this article does not adopt it. But the general risk is real in public-sector work. An adviser can be valued for reassurance as well as for analysis, and the two purposes can pull in different directions when the evidence becomes uncomfortable.
The defence against that risk is to agree measurable outcomes at the start, even when the client’s motives are mixed. If an engagement is meant to reduce violence, it should state how violence will be measured, against which baseline, over what period and with what data checks. Those commitments protect the adviser as much as the client, because they make it possible to show what the work did and did not achieve.
Outcomes for the whole system need careful attribution
ProPublica’s comparison of 2019 with 2014 found inmate attacks and use of force up 25% and assaults on staff up 15% by the city’s data, and violence up nearly 50% using McKinsey’s own metrics. These are serious findings about the jail system. They are not, by themselves, a measurement of what any single programme caused, because staffing, population, policy and leadership all changed over the same period.
That limitation cuts both ways. It means the later rise cannot simply be blamed on the advisers. It also means early pilot gains could not be credited to them without a clean comparison. Reporting a whole-system outcome next to a programme’s fee invites a causal reading that the data cannot support. The ICE detention-budget case raises a related point about distinguishing what an adviser recommended from what a public body implemented.
Spend analytics money only on tools that will be used
The IntelWatch tool, as reported, was paid for but never used. That outcome is common in analytics projects and is not unique to this engagement. It usually reflects a gap between what a technical team can build and what the client organisation is ready to operate, maintain and trust. Before funding a new model, ask who will use it daily, what decisions it will change, what data it needs and who will fix it when it fails.
Write those answers into the business case and test them before the build is complete. The business case calculator and the management consulting presentation guide can help set out the costs, the decision the tool supports and the evidence that will show whether it works. In a setting as consequential as a jail, an unused tool is not a neutral outcome. It is money and attention that could have gone elsewhere.
TAKE IT INTO THE NEXT MEETING
Three practical lessons
A hand-picked pilot proves little
If participants are chosen for good behaviour, an improvement may reflect the selection. Fix the selection rule in advance, log every exception and compare like with like.
Treat data concerns as signals
When several people closest to the data question it, pause the announcement and test the numbers. Record the concern and how it was resolved.
Be clear about why you were hired
If an engagement is valued partly for the reassurance it provides, define measurable outcomes anyway, so fees and results can be compared honestly.
Questions about the case
Did McKinsey falsify violence data at Rikers?
No court or regulator finding of that kind is described in the sources used here. ProPublica reported selection and data concerns. McKinsey denies that its consultants were involved in or aware of efforts to improperly skew reported violence, and City Hall said consultants were not involved in final housing decisions.
What was the Restart programme?
Restart was a type of housing unit introduced under the city’s 2015 anti-violence plan. By July 2015 eight units held about 250 people at the George Motchan Detention Center. They also tested McKinsey’s Housing Unit Balancer, a model meant to spread the risk of violence across units.
How much did New York pay McKinsey?
ProPublica reported $27.5 million in total, beginning with a $1.8 million contract in September 2014, with about $5.5 million for data analytics. The New York Daily News reported a different first-contract figure; ProPublica’s figures are used here.
THE EVIDENCE TRAIL
Sources & editorial notes
Adapted from the original XLSlides documentary, with additional analysis. Published 7 November 2026. Sources have different roles: primary records, investigative reporting and the positions of affected parties.
- ProPublica: New York City paid McKinsey millions to stem jail violence. Instead, violence soared. 10 December 2019 ↗Principal investigation, based on 36 interviews and more than 10,000 pages of project documents; includes McKinsey’s, City Hall’s and the department’s responses.
- New York Daily News, via Corrections1: staff concerns about Restart data, 10 September 2019 ↗Syndicated reporting of internal emails, the oversight-board claim, a 2017 payment and the monitor’s documentation concern.
- Prison Legal News: New York City paid McKinsey millions for a failed programme, 1 April 2020 ↗Advocacy-press cross-check of the contract history and early Restart figures.
- Nunez v. City of New York: Tenth Monitor’s Report, filed 23 October 2020 ↗Primary court-monitor report: the 2015 consent judgment and use-of-force findings for January–June 2020.
- CBS News: New York City Council votes to close Rikers, 17 October 2019 ↗Report of the 36–13 vote and the $8.7bn borough-jails plan.
- Wikipedia: Rikers Island ↗Background only, for 2015 budget, staffing and population figures; not used for any allegation.
Image credits & licences
Original illustrations and typography: XLSlides. Documentary stills have been resized and converted to WebP for this article. Underlying images retain the credits supplied with the episode.
- XLSlides logo: XLSlides.
- McKinsey & Company logo: public domain (text logo).
- ProPublica logo: public domain (text logo).
- The NYC Department of Correction is shown as a typeset name card; people (Bill de Blasio, Joseph Ponte, Steve J. Martin) as silhouettes. Rikers Island is a stylised drawing, not a map. Everything else is drawn; scenes marked "illustrative" are not to scale.
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