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How K-12 School Openings Without Masks Increased COVID-19 Cases

Apr 09, 2021 by Placekey

The seminar above covers the main topics discussed in The Association of Opening K-12 Schools and Colleges with the Spread of COVID-19 in the United States: County-Level Panel Data Analysis, authored by Victor Chernozhukov, Hiroyuki Kasahara, and Paul Schrimpf.

Leveraging location, address, and foot traffic data from Safegraph and Placekey, Hiroyuki Kasahara, Paul Schrimpf, and Victor Chernozhukov examine the relationship between the opening of K-12 schools and colleges and the spread of COVID-19. 

In the seminar, Hiroyuki Kasahara provides a summary of their findings and discusses the implications of these findings on informing sound COVID-19 prevention policies. Furthermore, they highlight how Safegraph and Placekey allowed them to use foot traffic and location data to account for travel with accuracy and confidence.


In-person education policies and no mask requirements lead to a growth in COVID-19 cases

This paper examines the impact opening K-12 schools had on the spread of COVID-19. Researchers use county-level policy data in the United States, school opening plans, and leverage location, address, and foot traffic data from Safegraph and Placekey to determine the average growth in case rates due to school openings.

They account for variables such as different teaching methods (in-person, hybrid, and remote), mask requirements for staff, full-time and part-time work visits, and restaurant and bar visits to see how these affect the spread of COVID-19. 

The conclusion is that in-person models of schooling have higher case growth rates and that mandatory masks and bans on gatherings help reduce the spread of COVID-19.

They also summarize their main findings on the impact K-12 school openings with no mask requirements had on the spread of COVID-19 in a VOXEU article, a leading source for commentary from prominent economists and research-based policy analysis. 

From the entire seminar, there are 5 main takeaways to consider when developing policies to reduce the spread of COVID-19 in schools and colleges, which are covered below in detail.


5 key takeaways from this seminar on the impact of school openings on COVID-19 case growth rates

By considering a number of variables, Chernozhukov, Kasahara, and Schrimpf are able to examine how school opening plans and policies, mask mandates, and full-time work travel impact the spread of COVID-19. By examining county-level data and leveraging location and foot traffic data from Safegraph and Placekey, they are able to effectively isolate the impact these different variables have on the spread of COVID-19.

Their conclusions find that in-person and hybrid learning models without strict COVID-19 safety guidelines (mask mandates for staff, social distancing, and hand sanitizing) lead to an increase in COVID-19 case rates. Their analysis also shows that masks being required of staff greatly reduce the spread of COVID-19, as does remote learning.

1. School opening models impact the spread of COVID-19

Image Credit: Taken from Figure 1 of The Association of Opening K-12 Schools and Colleges with the Spread of COVID-19 in the United States: County-Level Panel Data Analysis

Time in seminar video: 4:45

To study the impact school opening models had on the spread of COVID-19, they compared three main school opening models used:

  1. In-person: Students return to in-person learning.
  2. Hybrid: Students use a combination of in-person and remote learning.
  3. Remote: Students perform school remotely from home.

Their analysis found that the more interaction people had, the greater the growth in COVID-19 case and death rates. In general, remote school openings had the lowest growth rates, hybrid learning had higher growth rates, and in-person learning had the highest growth rates. 

This supports the theory that remote schooling models are the best at limiting the spread of COVID-19, and that any school attendance resulted in increased COVID-19 case growth rates.

2. Mask mandates for staff reduce the spread of COVID-19 in schools

Time in seminar video: 7:00

When examining the impact school opening plans had on COVID-19 growth rates, they also factored in a very important variable - mask mandates for staff. They used this to further break down the case opening models to include these variables:

  • In-person (with no mask mandate for staff)
  • In-person (with a mask mandate for staff)
  • Hybrid (with no mask mandate for staff)
  • Hybrid (with a mask mandate for staff)

What was so interesting about this distinction was that COVID-19 cases grew at a faster rate for hybrid learning with no mask mandate than it did for in-person learning with a mask mandate. This evidence suggests that mask mandates for staff had a significant impact on the spread of COVID-19 within schools and colleges. This evidence supports the fact that mask mandates are effective at curbing the COVID-19 case growth rate.

3. Remote school opening models had the lowest COVID-19 case growth rates

Time in seminar video: 7:14

Kasahara, Chernozhukov, and Schimpf also looked at school opening plans more closely, by examining actual K-12 school visits. This was made possible with location and foot traffic data provided by Placekey and Safegraph, which allows for identifying the number of visits to K-12 schools and colleges, as well as travel to restaurants and bars with accuracy.

Their findings show that remote openings lead to a very minimal increase in COVID-19 cases. Similarly, Hybrid learning with mask mandates had a very low rate of COVID-19 case growth. Alternatively, in-person (both with and without a mask mandate) and hybrid learning with no mask mandate had much higher COVID-19 growth rates, with much less differentiation. This proves that in-person schooling leads to the highest COVID-19 case growth rate.

4. Full-time work visits significantly increase COVID-19 case growth rates

Image Credit: Taken from Figure 1 of The Association of Opening K-12 Schools and Colleges with the Spread of COVID-19 in the United States: County-Level Panel Data Analysis

Time in seminar video: 8:05

Another variable considered was full-time workplace visits, defined by a cellular device visiting a location other than the home for a period of 6 hours or longer. This examines the impact these full-time workplace visits (and, in contrast, stay-at-home orders) have on the growth rate of COVID-19.

The main takeaway from this is that there are two clear mechanisms that lead to the spread of COVID-19, the first of which is in-school transmission. The second is a little more complicated - that school openings lead to parents being more mobile, as they are no longer staying home and are traveling to and from work. This mobility (and the implied contact that stems from this) leads to increased spread of COVID-19.

5. Bar and restaurant visits increase COVID-19 case rates in colleges

Image Credit: Taken from Figure 1 of The Association of Opening K-12 Schools and Colleges with the Spread of COVID-19 in the United States: County-Level Panel Data Analysis

Time in seminar video: 9:58

While the main focus was K-12, Chernozhukov, Kasahara, and Schimpf’s study also considered the impact college visits had on the spread of COVID-19 cases. By studying two separate counties, they determined a direct correlation between college visits and increases in COVID-19 rates.

As part of this study, they accounted for typical college student behavior, including visits to restaurants and bars. Their findings showed that visits to bars and restaurants directly correlated with an increase in COVID-19 cases. Their study focused on analyzing how this impacted the spread of COVID-19 across schools — in this case colleges.


How Safegraph and Placekey enabled research on COVID-19 transmission in schools

To facilitate their findings, Chernozhukov, Kasahara, and Schrimpf relied on location and foot traffic data made possible with Safegraph and Placekey.

SafeGraph is a point of interest (POI) and foot traffic data solution that provides device location data along with point of interest information. These features allow you to analyze interaction with POIs based on device locations, and examine a variety of information at once.

Placekey is a universal location identifier that encodes latitude and longitude data into an easy-to-use alphanumeric code. This makes address matching, address standardization, and even cross-referencing location and other point of interest information extremely fast and simple.


The authors’ backstories & research

Victor Chernozhukov is a Professor in the Department of Economics and the MIT Statistics and Data Science Center. He obtained his Ph.D. in Economics from Stanford University in 2000. His research areas include non-regular models, partial identification, set inference, policy analysis, big data, and central limit theorems.

Hiroyuki Kasahara is a professor at the Vancouver School of Economics at the University of British Columbia. He obtained his Ph.D. from the University of Wisconsin-Madison. He specializes in econometrics, international trade, and economic issues related to COVID-19. In his econometrics work, his research interests are primarily structural estimation, finite mixture models, nonparametric identification, and causal inference.

Paul Schrimpf is an associate professor at the Vancouver School of Economics at the University of British Columbia. He specializes in theoretical and applied econometrics, currently applying this to projects about dynamic games, partial identification, and insurance.



Ultimately, their observational study concluded that opening K-12 schools and colleges leads to an increase in the spread of COVID-19 cases, especially when mitigation strategies such as mask mandates are not employed. 

All of this is made possible with accurate location, point of interest, and foot traffic data facilitated by Safegraph and Placekey. These solutions helped these researchers analyze travel and evaluate the impact this has on the spread of COVID-19.

To learn how you can leverage Placekey for your needs, join the Placekey community. As an open-source solution, the community is continually adding locations and improving functionality by creating new, better integrations.

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