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All together now: the most trustworthy covid-19 model is an ensemble

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All together now: the most trustworthy covid-19 model is an ensemble


Every week, teams each submit not only a point forecast predicting a single number outcome (say, that in one week there will be 500 deaths). They also submit probabilistic predictions that quantify the uncertainty by estimating the likelihood of the number of cases or deaths at intervals, or ranges, that get narrower and narrower, targeting a central forecast. For instance, a model might predict that there’s a 90 percent probability of seeing 100 to 500 deaths, a 50 percent probability of seeing 300 to 400, and 10 percent probability of seeing 350 to 360.

“It’s like a bull’s eye, getting more and more focused,” says Reich.

Funk adds: “The sharper you define the target, the less likely you are to hit it.” It’s fine balance, since an arbitrarily wide forecast will be correct, and also useless. “It should be as precise as possible,” says Funk, “while also giving the correct answer.”

In collating and evaluating all the individual models, the ensemble tries to optimize their information and mitigate their shortcomings. The result is a probabilistic prediction, statistical average, or a “median forecast.” It’s a consensus, essentially, with a more finely calibrated, and hence more realistic, expression of the uncertainty. All the various elements of uncertainty average out in the wash.

The study by Reich’s lab, which focused on projected deaths and evaluated about 200,000 forecasts from mid-May to late-December 2020 (an updated analysis with predictions for four more months will soon be added), found that the performance of individual models was highly variable. One week a model might be accurate, the next week it might be way off. But, as the authors wrote, “In combining the forecasts from all teams, the ensemble showed the best overall probabilistic accuracy.”

And these ensemble exercises serve not only to improve predictions, but also people’s trust in the models, says Ashleigh Tuite, an epidemiologist at the Dalla Lana School of Public Health at the University of Toronto. “One of the lessons of ensemble modeling is that none of the models is perfect,” Tuite says. “And even the ensemble sometimes will miss something important. Models in general have a hard time forecasting inflection points—peaks, or if things suddenly start accelerating or decelerating.”

“Models are not oracles.”

Alessandro Vespignani

The use of ensemble modeling is not unique to the pandemic. In fact, we consume probabilistic ensemble forecasts every day when Googling the weather and taking note that there’s 90 percent chance of precipitation. It’s the gold standard for both weather and climate predictions.

“It’s been a real success story and the way to go for about three decades,” says Tilmann Gneiting, a computational statistician at the Heidelberg Institute for Theoretical Studies and the Karlsruhe Institute of Technology in Germany. Prior to ensembles, weather forecasting used a single numerical model, which produced, in raw form, a deterministic weather forecast that was “ridiculously overconfident and wildly unreliable,” says Gneiting (weather forecasters, aware of this problem, subjected the raw results to subsequent statistical analysis that produced reasonably reliable probability of precipitation forecasts by the 1960s).

Gneiting notes, however, that the analogy between infectious disease and weather forecasting has its limitations. For one thing, the probability of precipitation doesn’t change in response to human behavior—it’ll rain, umbrella or no umbrella—whereas the trajectory of the pandemic responds to our preventative measures.

Forecasting during a pandemic is a system subject to a feedback loop. “Models are not oracles,” says Alessandro Vespignani, a computational epidemiologist at Northeastern University and ensemble hub contributor, who studies complex networks and infectious disease spread with a focus on the “techno-social” systems that drive feedback mechanisms. “Any model is providing an answer that is conditional on certain assumptions.”

When people process a model’s prediction, their subsequent behavioral changes upend the assumptions, change the disease dynamics and render the forecast inaccurate. In this way, modeling can be a “self-destroying prophecy.”

And there are other factors that could compound the uncertainty: seasonality, variants, vaccine availability or uptake; and policy changes like the swift decision from the CDC about unmasking. “These all amount to huge unknowns that, if you actually wanted to capture the uncertainty of the future, would really limit what you could say,” says Justin Lessler, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, and a contributor to the COVID-19 Forecast Hub.

The ensemble study of death forecasts observed that accuracy decays, and uncertainty grows, as models make predictions farther into the future—there was about two times the error looking four weeks ahead versus one week (four weeks is considered the limit for meaningful short-term forecasts; at the 20-week time horizon there was about five times the error).

“It’s fair to debate when things worked and when things didn’t.”

Johannes Bracher

But assessing the quality of the models—warts and all—is an important secondary goal of forecasting hubs. And it’s easy enough to do, since short-term predictions are quickly confronted with the reality of the numbers tallied day-to-day, as a measure of their success.

Most researchers are careful to differentiate between this type of “forecast model,” aiming to make explicit and verifiable predictions about the future, which is only possible in the short- term; versus a “scenario model,” exploring “what if” hypotheticals, possible plotlines that might develop in the medium- or long-term future (since scenario models are not meant to be predictions, they shouldn’t be evaluated retrospectively against reality).

During the pandemic, a critical spotlight has often been directed at models with predictions that were spectacularly wrong. “While longer-term what-if projections are difficult to evaluate, we shouldn’t shy away from comparing short-term predictions with reality,” says Johannes Bracher, a biostatistician at the Heidelberg Institute for Theoretical Studies and the Karlsruhe Institute of Technology, who coordinates a German and Polish hub, and advises the European hub. “It’s fair to debate when things worked and when things didn’t,” he says. But an informed debate requires recognizing and considering the limits and intentions of models (sometimes the fiercest critics were those who mistook scenario models for forecast models).

“The big question is, can we improve?”

Nicholas Reich

Similarly, when predictions in any given situation prove particularly intractable, modelers should say so. “If we have learned one thing, it’s that cases are extremely difficult to model even in the short run,” says Bracher. “Deaths are a more lagged indicator and are easier to predict.”

In April, some of the European models were overly pessimistic and missed a sudden decrease in cases. A public debate ensued about the accuracy and reliability of pandemic models. Weighing in on Twitter, Bracher asked: “Is it surprising that the models are (not infrequently) wrong? After a 1-year pandemic, I would say: no.”  This makes it all the more important, he says, that models indicate their level of certainty or uncertainty, that they take a realistic stance about how unpredictable cases are, and about the future course. “Modelers need to communicate the uncertainty, but it shouldn’t be seen as a failure,” Bracher says.

Trusting some models more than others

As an oft-quoted statistical aphorism goes, “All models are wrong, but some are useful.” But as Bracher notes, “If you do the ensemble model approach, in a sense you are saying that all models are useful, that each model has something to contribute”—though some models may be more informative or reliable than others.

Observing this fluctuation prompted Reich and others to try “training” the ensemble model—that is, as Reich explains, “building algorithms that teach the ensemble to ‘trust’ some models more than others and learn which precise combination of models works in harmony together.” Bracher’s team now contributes a mini-ensemble, built from only the models that have performed consistently well in the past, amplifying the clearest signal.

“The big question is, can we improve?” Reich says. “The original method is so simple. It seems like there has to be a way of improving on just taking a simple average of all these models.” So far, however, it is proving harder than expected—small improvements seem feasible, but dramatic improvements may be close to impossible.

A complementary tool for improving our overall perspective on the pandemic beyond week-to-week glimpses is to look further out on the time horizon, four to six months, with those “scenario modeling.” Last December, motivated by the surge in cases and the imminent availability of the vaccine, Lessler and collaborators launched the COVID-19 Scenario Modeling Hub, in consultation with the CDC.

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Rediscover trust in cybersecurity

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Rediscover trust in cybersecurity


The world has changed dramatically in a short amount of time—changing the world of work along with it. The new hybrid remote and in-office work world has ramifications for tech—specifically cybersecurity—and signals that it’s time to acknowledge just how intertwined humans and technology truly are.

Enabling a fast-paced, cloud-powered collaboration culture is critical to rapidly growing companies, positioning them to out innovate, outperform, and outsmart their competitors. Achieving this level of digital velocity, however, comes with a rapidly growing cybersecurity challenge that is often overlooked or deprioritized : insider risk, when a team member accidentally—or not—shares data or files outside of trusted parties. Ignoring the intrinsic link between employee productivity and insider risk can impact both an organizations’ competitive position and its bottom line. 

You can’t treat employees the same way you treat nation-state hackers

Insider risk includes any user-driven data exposure event—security, compliance or competitive in nature—that jeopardizes the financial, reputational or operational well-being of a company and its employees, customers, and partners. Thousands of user-driven data exposure and exfiltration events occur daily, stemming from accidental user error, employee negligence, or malicious users intending to do harm to the organization. Many users create insider risk accidentally, simply by making decisions based on time and reward, sharing and collaborating with the goal of increasing their productivity. Other users create risk due to negligence, and some have malicious intentions, like an employee stealing company data to bring to a competitor. 

From a cybersecurity perspective, organizations need to treat insider risk differently than external threats. With threats like hackers, malware, and nation-state threat actors, the intent is clear—it’s malicious. But the intent of employees creating insider risk is not always clear—even if the impact is the same. Employees can leak data by accident or due to negligence. Fully accepting this truth requires a mindset shift for security teams that have historically operated with a bunker mentality—under siege from the outside, holding their cards close to the vest so the enemy doesn’t gain insight into their defenses to use against them. Employees are not the adversaries of a security team or a company—in fact, they should be seen as allies in combating insider risk.

Transparency feeds trust: Building a foundation for training

All companies want to keep their crown jewels—source code, product designs, customer lists—from ending up in the wrong hands. Imagine the financial, reputational, and operational risk that could come from material data being leaked before an IPO, acquisition, or earnings call. Employees play a pivotal role in preventing data leaks, and there are two crucial elements to turning employees into insider risk allies: transparency and training. 

Transparency may feel at odds with cybersecurity. For cybersecurity teams that operate with an adversarial mindset appropriate for external threats, it can be challenging to approach internal threats differently. Transparency is all about building trust on both sides. Employees want to feel that their organization trusts them to use data wisely. Security teams should always start from a place of trust, assuming the majority of employees’ actions have positive intent. But, as the saying goes in cybersecurity, it’s important to “trust, but verify.” 

Monitoring is a critical part of managing insider risk, and organizations should be transparent about this. CCTV cameras are not hidden in public spaces. In fact, they are often accompanied by signs announcing surveillance in the area. Leadership should make it clear to employees that their data movements are being monitored—but that their privacy is still respected. There is a big difference between monitoring data movement and reading all employee emails.

Transparency builds trust—and with that foundation, an organization can focus on mitigating risk by changing user behavior through training. At the moment, security education and awareness programs are niche. Phishing training is likely the first thing that comes to mind due to the success it’s had moving the needle and getting employees to think before they click. Outside of phishing, there is not much training for users to understand what, exactly, they should and shouldn’t be doing.

For a start, many employees don’t even know where their organizations stand. What applications are they allowed to use? What are the rules of engagement for those apps if they want to use them to share files? What data can they use? Are they entitled to that data? Does the organization even care? Cybersecurity teams deal with a lot of noise made by employees doing things they shouldn’t. What if you could cut down that noise just by answering these questions?

Training employees should be both proactive and responsive. Proactively, in order to change employee behavior, organizations should provide both long- and short-form training modules to instruct and remind users of best behaviors. Additionally, organizations should respond with a micro-learning approach using bite-sized videos designed to address highly specific situations. The security team needs to take a page from marketing, focusing on repetitive messages delivered to the right people at the right time. 

Once business leaders understand that insider risk is not just a cybersecurity issue, but one that is intimately intertwined with an organization’s culture and has a significant impact on the business, they will be in a better position to out-innovate, outperform, and outsmart their competitors. In today’s hybrid remote and in-office work world, the human element that exists within technology has never been more significant.That’s why transparency and training are essential to keep data from leaking outside the organization. 

This content was produced by Code42. It was not written by MIT Technology Review’s editorial staff.

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How AI is reinventing what computers are

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How AI is reinventing what computers are


Fall 2021: the season of pumpkins, pecan pies, and peachy new phones. Every year, right on cue, Apple, Samsung, Google, and others drop their latest releases. These fixtures in the consumer tech calendar no longer inspire the surprise and wonder of those heady early days. But behind all the marketing glitz, there’s something remarkable going on. 

Google’s latest offering, the Pixel 6, is the first phone to have a separate chip dedicated to AI that sits alongside its standard processor. And the chip that runs the iPhone has for the last couple of years contained what Apple calls a “neural engine,” also dedicated to AI. Both chips are better suited to the types of computations involved in training and running machine-learning models on our devices, such as the AI that powers your camera. Almost without our noticing, AI has become part of our day-to-day lives. And it’s changing how we think about computing.

What does that mean? Well, computers haven’t changed much in 40 or 50 years. They’re smaller and faster, but they’re still boxes with processors that run instructions from humans. AI changes that on at least three fronts: how computers are made, how they’re programmed, and how they’re used. Ultimately, it will change what they are for. 

“The core of computing is changing from number-crunching to decision-­making,” says Pradeep Dubey, director of the parallel computing lab at Intel. Or, as MIT CSAIL director Daniela Rus puts it, AI is freeing computers from their boxes. 

More haste, less speed

The first change concerns how computers—and the chips that control them—are made. Traditional computing gains came as machines got faster at carrying out one calculation after another. For decades the world benefited from chip speed-ups that came with metronomic regularity as chipmakers kept up with Moore’s Law. 

But the deep-learning models that make current AI applications work require a different approach: they need vast numbers of less precise calculations to be carried out all at the same time. That means a new type of chip is required: one that can move data around as quickly as possible, making sure it’s available when and where it’s needed. When deep learning exploded onto the scene a decade or so ago, there were already specialty computer chips available that were pretty good at this: graphics processing units, or GPUs, which were designed to display an entire screenful of pixels dozens of times a second. 

Anything can become a computer. Indeed, most household objects, from toothbrushes to light switches to doorbells, already come in a smart version.

Now chipmakers like Intel and Arm and Nvidia, which supplied many of the first GPUs, are pivoting to make hardware tailored specifically for AI. Google and Facebook are also forcing their way into this industry for the first time, in a race to find an AI edge through hardware. 

For example, the chip inside the Pixel 6 is a new mobile version of Google’s tensor processing unit, or TPU. Unlike traditional chips, which are geared toward ultrafast, precise calculations, TPUs are designed for the high-volume but low-­precision calculations required by neural networks. Google has used these chips in-house since 2015: they process people’s photos and natural-­language search queries. Google’s sister company DeepMind uses them to train its AIs. 

In the last couple of years, Google has made TPUs available to other companies, and these chips—as well as similar ones being developed by others—are becoming the default inside the world’s data centers. 

AI is even helping to design its own computing infrastructure. In 2020, Google used a reinforcement-­learning algorithm—a type of AI that learns how to solve a task through trial and error—to design the layout of a new TPU. The AI eventually came up with strange new designs that no human would think of—but they worked. This kind of AI could one day develop better, more efficient chips. 

Show, don’t tell

The second change concerns how computers are told what to do. For the past 40 years we have been programming computers; for the next 40 we will be training them, says Chris Bishop, head of Microsoft Research in the UK. 

Traditionally, to get a computer to do something like recognize speech or identify objects in an image, programmers first had to come up with rules for the computer.

With machine learning, programmers no longer write rules. Instead, they create a neural network that learns those rules for itself. It’s a fundamentally different way of thinking. 

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Decarbonizing industries with connectivity and 5G

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Decarbonizing industries with connectivity and 5G


The United Nations Intergovernmental Panel on Climate Change’s sixth climate change report—an aggregated assessment of scientific research prepared by some 300 scientists across 66 countries—has served as the loudest and clearest wake-up call to date on the global warming crisis. The panel unequivocally attributes the increase in the earth’s temperature—it has risen by 1.1 °C since the Industrial Revolution—to human activity. Without substantial and immediate reductions in carbon dioxide and other greenhouse gas emissions, temperatures will rise between 1.5 °C and 2 °C before the end of the century. That, the panel posits, will lead all of humanity to a “greater risk of passing through ‘tipping points,’ thresholds beyond which certain impacts can no longer be avoided even if temperatures are brought back down later on.”

Corporations and industries must therefore redouble their greenhouse gas emissions reduction and removal efforts with speed and precision—but to do this, they must also commit to deep operational and organizational transformation. Cellular infrastructure, particularly 5G, is one of the many digital tools and technology-enabled processes organizations have at their disposal to accelerate decarbonization efforts.  

5G and other cellular technology can enable increasingly interconnected supply chains and networks, improve data sharing, optimize systems, and increase operational efficiency. These capabilities could soon contribute to an exponential acceleration of global efforts to reduce carbon emissions.

Industries such as energy, manufacturing, and transportation could have the biggest impact on decarbonization efforts through the use of 5G, as they are some of the biggest greenhouse-gas-emitting industries, and all rely on connectivity to link to one another through communications network infrastructure.

The higher performance and improved efficiency of 5G—which delivers higher multi-gigabit peak data speeds, ultra-low latency, increased reliability, and increased network capacity—could help businesses and public infrastructure providers focus on business transformation and reduction of harmful emissions. This requires effective digital management and monitoring of distributed operations with resilience and analytic insight. 5G will help factories, logistics networks, power companies, and others operate more efficiently, more consciously, and more purposely in line with their explicit sustainability objectives through better insight and more powerful network configurations.

This report, “Decarbonizing industries with connectivity & 5G,” argues that the capabilities enabled by broadband cellular connectivity primarily, though not exclusively, through 5G network infrastructure are a unique, powerful, and immediate enabler of carbon reduction efforts. They have the potential to create a transformational acceleration of decarbonization efforts, as increasingly interconnected supply chains, transportation, and energy networks share data to increase efficiency and productivity, hence optimizing systems for lower carbon emissions.

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