COVID Data: Where to Get It and How to Read It

Emily Oster

9 min Read Emily Oster

Emily Oster

COVID Data: Where to Get It and How to Read It

Emily Oster

9 min Read

My own data collection efforts continue. If you do want to help contribute to the child care data, as imperfect as it is, check out the constantly updated COVID-Explained post here. Lots of notes there on what data we have, and how you can help us get more. We’ve included a draft letter to send to your provider. We’d love to start including more schools and camps.

Data Sources: What are they and How to Understand Them

I was planning this post last week, and then of course this weekend our President said that we should do less testing since we’d then have less infections and my head exploded a little bit. So let’s start this by saying that doing less testing WILL NOT PRODUCE FEWER INFECTIONS. This isn’t how it works.

If it were not so important, it would be a great introductory stats example for confusing the direction of causality. You see more testing and more cases move together, and you assume the testing is driving the cases. Students could explain why this makes no sense.

So, this idea is ridiculous. But in practice it is the case that with our current data availability, tracking the epidemic is hard. What’s the best way to do it? To think about this, we’ll start with the first question: Why do you want to know? And then check out where we can find data, and how to read them.

Why do you want to know?

There are a few reasons why one might want data on the pandemic. One is to study different policy responses and which worked; this is probably a task for a much later, future, time. Another reason is to track whether hospitals are getting overwhelmed and try to prepare.

From the standpoint of an individual, though, I think the main reason we might want data is to figure out how much spread there is in our community so we can decide on our level of external engagement. When we think about how much to get out, it clearly matters if the COVID-19 rate in our area is 1%, or 10% or 0.1% since that impacts the chance that we encounter someone with the virus.

So for this post I really want to focus in on this question: how can I best understand the current viral level in my location so I can make good choices? Questions like: What’s the best way for states to track their progress and protect their hospitals? I will leave for another day.

What would be ideal?

Best case scenario would be random or universal testing of everyone, symptoms or not. I wrote about why in an earlier newsletter here. The bottom line is that if we sampled people randomly and tested them, we’d be able to get a sense of the level of infection in the population, including anyone without symptoms or with mild symptoms.

As companies start to return to work and universities contemplate their return to campus, I think we will start seeing more testing like this in certain populations (for example, see some discussions here). But we do not have it yet.

Where’s the Data we do Have?

Perhaps surprisingly, this is the easier question than how to interpret it. The best tracking data on the pandemic comes from Johns Hopkins. You can check out their site here. There is a tremendous amount on the site, and they have excellent data on testing and tracking, and their case count data is down to the county level in many places.

The other excellent source is the New York Times although some pieces are behind a paywall. They also do not have an obvious place where they report number of tests. These data are easier to read but less comprehensive.

Individuals states also have some of their own data. For example, if you live in Rhode Island, you can check out all our data here!

What data should I pay attention to?

We have basically four pieces of data that you could look at.

  • Deaths
  • Hospitalizations
  • Number of cases (positive tests)
  • Total number of tests run

Of these, the first two are the least complicated to understand and the most reliable. It’s not perfect, but we generally do a good job of recording deaths. Similarly, hospitalizations are fairly well reported in most areas and we know COVID-19 status for most hospitalized patients.

When we go back to analyze the pandemic from the standpoint of the future, I suspect these are the data we will use most extensively. However: from the standpoint of current decision-making, the timing of these data are not great. For your choices, you want to know how many people have the virus now. Generally we think hospitalizations will lag cases by a couple of weeks, and deaths by perhaps a month. Basically, by the time you see a lot of people in the hospital, it has been several weeks of high case rates.

For current tracking, the best we can do is data on case counts, which comes from tests. You can access data for your state from Johns Hopkins.

The first set of pictures is number of positive cases, the second is counts of tests per person and the third is the share of tests that are positive.

What you want to know is: of all the people around, what share of them carry the coronavirus? This is really the decision relevant information. The question is: how much can you learn about this thing you’re interested in from the information in the above graphs?

Based on the data we have, there are really two things that you could rely on: (1) the number of positive tests (sometimes called “the case count”, the thing most commonly reported) or (2) the share of tests which are positive. Neither is quite right, although the biases are in opposite directions.

To start, think about the case counts. Let’s imagine 10% of people in some population have the virus, and you test 200 of them. You’ll get 20 cases. Now test 2000 of the. You’ll get 200 cases. Now test 20,000 of them. You’ll get 2000 cases. The decision-relevant thing — the share of people with the virus — hasn’t changed. But your case counts have gone up a lot.

What this means is that as you test more, you’ll get more cases. Conversely, if you test less, you’ll detect fewer cases. This does not mean the virus is less prevalent. (In fact, testing is really, really important since it allows us to detect and isolate asymptomatic positive people.) What this does mean is that as places test more, we expect them to detect more cases and it doesn’t necessarily mean the virus is getting more prevalent.

Now let’s think about our other quantity, the share of positive tests. You could say: “We tested people, and only 1% of them were positive”, and you might well perceive this as being better than seeing 10% positive or 20% positive. And if we were testing people randomly, this would be exactly the right number to report and would tell us what we want to know.

BUT: in practice, testing is not random and typically the highest risk people are tested first. If you had a shortage of tests, as many places had and still do, you would likely not use them on healthy people. What this means is that the share of positive tests is typically higher when there are fewer of them. Note that this is not mechanical the way that the tests and case counts are. It isn’t necessarily true. But in practice, this is the the pattern just given the way tests are used.

What we tend to see, then, is that as places increase their testing the share of positive tests go down. This is good in the sense that it’s getting closer to capturing the actual population level rate, but it’s worth being cautious about the trends in this over time. It can be tempting to conclude that the virus is diminishing — which it might be! — but it could reflect changes in the tested population.

Bottom line, though — what should you be looking at, if nothing is perfect? If you live in a state with a fairly robust testing program — that is, they are doing a lot of tests, and a pretty consistent number per day — then my sense is the best thing to look at is the share of tests which are positive. This will come closest to the figure you care about.

For example: In the Johns Hopkins data for Florida, tests are very flat at around 1.3 per 1000 people, and the share positive is going up sharply. This tells you the epidemic is getting worse. Case counts are going up, sure, but it looks like rates are too.

In Illinois, things look a lot better. Testing rates are pretty flat and the share positive is falling fast.

Much harder to learn from is a place like South Carolina. Tests have increased a lot. Cases are going up. Share positive is all over the map. Even putting aside the fact that the big spike must be some kind of odd reporting thing, the fact that the share positive has declined in the last week may reflect the fact that they are testing more.

Hope this helps a bit. Or that you are now so confused you storm down to your local State legislature and demand that the state do better universal or random testing. Either way.

Covid-19 rapid antigen tests arranged in a pattern on a yellow background.

Feb 20 2023

12 min read

COVID-19: Where to Go from Here

A long-term view of the virus

Emily Oster
Covid-19 rapid antigen tests arranged in a pattern on a yellow background.

Oct 20 2022

9 min read

Should You Get the Bivalent Booster?

The latest on the risks and benefits of COVID vaccines boosters for older adults, pregnant people, and kids

Emily Oster
A line graph with pink, yellow, and blue dots representing life's ups and downs.

Aug 16 2022

3 min read

Wins, Woes, and Doing It Again

We have our first story from a dad! And it’s a good one. 10/10 —Girl Dad with Confidence Growing by Read more

Emily Oster
Covid-19 rapid antigen tests arranged in a pattern on a yellow background.

Aug 15 2022

8 min read

Updated CDC Guidelines for School and Child Care

NO QUARANTINES!!!

Emily Oster

Instagram

left right
The AAP’s guidelines recommend sleeping in the same room as your baby “ideally for the first six months.” However, the risk of SIDS is dramatically lower after four months, and the evidence in favor of the protective effect of room sharing is quite weak (both overall and even more so after four months). There is also growing evidence that infants who sleep in their own room by four months sleep better at four months, better at nine months, and even better at 30 months.

With this in mind, it’s worth asking why this recommendation continues at all — or at least why the AAP doesn’t push it back to four months. They say decreased arousals from sleep are linked to SIDS, which could mean that babies sleeping in their own room is risky. But this link is extremely indirect, and they do not show direct evidence to support it.

According to the data we have, parents should sleep in the same room as a baby for as long as it works for them! Sharing a room with a child may have negative impacts on both child and adult sleep. We should give families more help in navigating these trade-offs and making the decisions that work best for them.

#emilyoster #parentdata #roomsharing #sids #parentingguide

The AAP’s guidelines recommend sleeping in the same room as your baby “ideally for the first six months.” However, the risk of SIDS is dramatically lower after four months, and the evidence in favor of the protective effect of room sharing is quite weak (both overall and even more so after four months). There is also growing evidence that infants who sleep in their own room by four months sleep better at four months, better at nine months, and even better at 30 months.

With this in mind, it’s worth asking why this recommendation continues at all — or at least why the AAP doesn’t push it back to four months. They say decreased arousals from sleep are linked to SIDS, which could mean that babies sleeping in their own room is risky. But this link is extremely indirect, and they do not show direct evidence to support it.

According to the data we have, parents should sleep in the same room as a baby for as long as it works for them! Sharing a room with a child may have negative impacts on both child and adult sleep. We should give families more help in navigating these trade-offs and making the decisions that work best for them.

#emilyoster #parentdata #roomsharing #sids #parentingguide
...

It was an absolute pleasure to be featured on the @tamronhallshow! We talked about all things data-driven parenting and, in this clip, what I call the plague of secret parenting. To balance having a career and having a family, we can’t hide the fact that we’re parents. If mothers and fathers at the top can speak more openly about child-care obligations, it will help us all set a new precedent.

Watch the full segment at the link in my bio 🔗

#tamronhall #tamronhallshow #emilyoster #parentingsupport #workingparents

It was an absolute pleasure to be featured on the @tamronhallshow! We talked about all things data-driven parenting and, in this clip, what I call the plague of secret parenting. To balance having a career and having a family, we can’t hide the fact that we’re parents. If mothers and fathers at the top can speak more openly about child-care obligations, it will help us all set a new precedent.

Watch the full segment at the link in my bio 🔗

#tamronhall #tamronhallshow #emilyoster #parentingsupport #workingparents
...

Invisible labor. It’s the work — in our households especially — that has to happen but that no one sees. It’s making the doctor’s appointment, ensuring birthday cards are purchased, remembering the milk.

My guest on this episode, @everodsky, has come up with a solution here, or at least a way for us to recognize the problem and make our own solutions. I’ve wanted to speak with Eve for ages, since I read her book Fair Play. We had a great conversation about the division of household labor, one I think you’ll get a lot out of!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#emilyoster #parentdata #parentdatapodcast #parentingpodcast #householdtips #fairplay #invisiblelabor

Invisible labor. It’s the work — in our households especially — that has to happen but that no one sees. It’s making the doctor’s appointment, ensuring birthday cards are purchased, remembering the milk.

My guest on this episode, @everodsky, has come up with a solution here, or at least a way for us to recognize the problem and make our own solutions. I’ve wanted to speak with Eve for ages, since I read her book Fair Play. We had a great conversation about the division of household labor, one I think you’ll get a lot out of!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#emilyoster #parentdata #parentdatapodcast #parentingpodcast #householdtips #fairplay #invisiblelabor
...

Prenatal vitamins 💊 If there is any product that seems designed to prey on our fears, it’s this one. You’re newly pregnant and you want to do it right. Everyone agrees you need prenatal vitamins, so you get them. But do you want to be that person who just… buys the generic prenatal vitamins?

Good news: fancier vitamins are not better.  Folic acid is the most important prenatal ingredient. Iron (with vitamin C) and DHA are also nice to have. Other included ingredients have only weak or no evidence to support their use. (If you do not consume animal products, add B12, plus a few others depending on your diet.)

Vitamins are just vitamins. Any prenatal vitamin that contains these is enough. 

Comment “Link” for a DM to an article with everything you need to know about prenatal vitamins.

#emilyoster #parentdata #prenatalvitamins #pregnancydiet #pregnancytips

Prenatal vitamins 💊 If there is any product that seems designed to prey on our fears, it’s this one. You’re newly pregnant and you want to do it right. Everyone agrees you need prenatal vitamins, so you get them. But do you want to be that person who just… buys the generic prenatal vitamins?

Good news: fancier vitamins are not better. Folic acid is the most important prenatal ingredient. Iron (with vitamin C) and DHA are also nice to have. Other included ingredients have only weak or no evidence to support their use. (If you do not consume animal products, add B12, plus a few others depending on your diet.)

Vitamins are just vitamins. Any prenatal vitamin that contains these is enough.

Comment “Link” for a DM to an article with everything you need to know about prenatal vitamins.

#emilyoster #parentdata #prenatalvitamins #pregnancydiet #pregnancytips
...

When it comes to introducing your newborn to the world, timing matters. It’s a good idea to minimize germ exposure in the first 6-8 weeks; after that, it’s inevitable and, very likely, a good idea! This doesn’t mean you need to be trapped inside. The most significant exposure risks are from seeing other people at home — family, etc. These interactions are not infinitely risky, but they do pose more risk than a walk or a trip to the grocery store, since they involve closer interaction. Think simple and make sure everyone is washing their hands before holding the baby. 💛

#parentdata #emilyoster #newborncare #parentingadvice #parentingtips

When it comes to introducing your newborn to the world, timing matters. It’s a good idea to minimize germ exposure in the first 6-8 weeks; after that, it’s inevitable and, very likely, a good idea! This doesn’t mean you need to be trapped inside. The most significant exposure risks are from seeing other people at home — family, etc. These interactions are not infinitely risky, but they do pose more risk than a walk or a trip to the grocery store, since they involve closer interaction. Think simple and make sure everyone is washing their hands before holding the baby. 💛

#parentdata #emilyoster #newborncare #parentingadvice #parentingtips
...

The first edition of Hot Flash is out now! Comment “Link” for a DM to learn more about the late-reproductive stage.

There are times when we expect hormonal shifts. Our reproductive lives are bookended by puberty and menopause. We discuss those changes often because they are definitive and dramatic — a first period is something many of us remember clearly. But between ages 13 and 53, our hormones are changing in more subtle ways. During the late-reproductive stage (in your 40s), you can expect a lot of changes in your menstrual cycle, including the length and symptoms you experience throughout. It’s an important time in our lives that is often overlooked!

🔥 Hot Flash from ParentData is a weekly newsletter on navigating your health and hormones in the post-reproductive years. Written by Dr. Gillian Goddard, Hot Flash provides all of the information you need to have a productive, evidence-based conversation about hormonal health with your doctor.

#emilyoster #parentdata #hotflash #perimenopause #womenshealth

The first edition of Hot Flash is out now! Comment “Link” for a DM to learn more about the late-reproductive stage.

There are times when we expect hormonal shifts. Our reproductive lives are bookended by puberty and menopause. We discuss those changes often because they are definitive and dramatic — a first period is something many of us remember clearly. But between ages 13 and 53, our hormones are changing in more subtle ways. During the late-reproductive stage (in your 40s), you can expect a lot of changes in your menstrual cycle, including the length and symptoms you experience throughout. It’s an important time in our lives that is often overlooked!

🔥 Hot Flash from ParentData is a weekly newsletter on navigating your health and hormones in the post-reproductive years. Written by Dr. Gillian Goddard, Hot Flash provides all of the information you need to have a productive, evidence-based conversation about hormonal health with your doctor.

#emilyoster #parentdata #hotflash #perimenopause #womenshealth
...

There are plenty of reels telling you how to parent. Plenty of panic headlines saying that “studies show” what’s best for your kid. Even good data, from a trusted source, can send us into a spiral of comparison. But I want you to remember that no one knows your kid better than you. It’s important to absorb the research, but only you will know the approach that works best for you and your child. 💙

Now tell me in the comments: what’s a parenting move you’ve made recently that feels right to you?

#parentingcommunity #parentingsupport #parentingquotes #emilyoster #parentdata

There are plenty of reels telling you how to parent. Plenty of panic headlines saying that “studies show” what’s best for your kid. Even good data, from a trusted source, can send us into a spiral of comparison. But I want you to remember that no one knows your kid better than you. It’s important to absorb the research, but only you will know the approach that works best for you and your child. 💙

Now tell me in the comments: what’s a parenting move you’ve made recently that feels right to you?

#parentingcommunity #parentingsupport #parentingquotes #emilyoster #parentdata
...

Let’s talk about sex (after) baby! Today on the podcast, I was lucky enough to speak with @enagoski about her new book on sexual connection in long-term relationships. Especially after having kids, this is something many people struggle with. Emily tells us to stop worrying about what’s “normal” and focus on pleasure in its many forms.

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #parentdatapodcast #emilyoster #emilynagoski #comeasyouare #cometogether #longtermrelationship #intimacy #relationships

Let’s talk about sex (after) baby! Today on the podcast, I was lucky enough to speak with @enagoski about her new book on sexual connection in long-term relationships. Especially after having kids, this is something many people struggle with. Emily tells us to stop worrying about what’s “normal” and focus on pleasure in its many forms.

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #parentdatapodcast #emilyoster #emilynagoski #comeasyouare #cometogether #longtermrelationship #intimacy #relationships
...

Ever wondered if you can safely use leftover baby formula? 🍼 The CDC says to throw out unused formula immediately because of the risk of bacterial growth. However, research suggests that bacterial concentrations do not appreciably increase after 3, 12, or even 24 hours at refrigerator temperatures. Good news! This means there’s not a strong data-based reason to throw out formula right away if you store it in the fridge.

Comment “Link” for a DM to an article on another common formula question: should you throw away old formula powder?

#emilyoster #parentdata #babyformula #babyfeeding #parentingstruggles

Ever wondered if you can safely use leftover baby formula? 🍼 The CDC says to throw out unused formula immediately because of the risk of bacterial growth. However, research suggests that bacterial concentrations do not appreciably increase after 3, 12, or even 24 hours at refrigerator temperatures. Good news! This means there’s not a strong data-based reason to throw out formula right away if you store it in the fridge.

Comment “Link” for a DM to an article on another common formula question: should you throw away old formula powder?

#emilyoster #parentdata #babyformula #babyfeeding #parentingstruggles
...

What’s the most important piece of advice for new parents? Here’s one answer, but I want to hear from you! Share your suggestions in the comments ⬇️

#emilyoster #parentdata #parentingtips #parentingadvice #newparents #parentingcommunity

What’s the most important piece of advice for new parents? Here’s one answer, but I want to hear from you! Share your suggestions in the comments ⬇️

#emilyoster #parentdata #parentingtips #parentingadvice #newparents #parentingcommunity
...

What's in the bag of a Vagina Economist? 👀 Someone please tell me this looks familiar to you.

What`s in the bag of a Vagina Economist? 👀 Someone please tell me this looks familiar to you. ...

Comment ”link” for a DM to learn more about tongue ties 🔗

Breastfeeding is often difficult, especially at the start. For babies with tongue ties, many infants (and their moms) struggle to get the hang of a good latch. This can lead to painful nipples and to inefficient feeding, and then low weight gain.

So what does the data say about the increasingly common practice of cutting tongue-ties in infants to improve breastfeeding success? Several weeks ago, @nytimes published a long and quite scary article on this topic.

After diving into the data, here is what I found. There is limited evidence that frenotomy procedures improve breastfeeding efficacy and the harms of the procedure are minimal. Many women do report that it alleviates pain and helps them with breastfeeding. However, it should not be a first-line treatment for breastfeeding problems.

#parentdata #emilyoster #tonguetie #tonguetiebabies #breastfeedingsupport

Comment ”link” for a DM to learn more about tongue ties 🔗

Breastfeeding is often difficult, especially at the start. For babies with tongue ties, many infants (and their moms) struggle to get the hang of a good latch. This can lead to painful nipples and to inefficient feeding, and then low weight gain.

So what does the data say about the increasingly common practice of cutting tongue-ties in infants to improve breastfeeding success? Several weeks ago, @nytimes published a long and quite scary article on this topic.

After diving into the data, here is what I found. There is limited evidence that frenotomy procedures improve breastfeeding efficacy and the harms of the procedure are minimal. Many women do report that it alleviates pain and helps them with breastfeeding. However, it should not be a first-line treatment for breastfeeding problems.

#parentdata #emilyoster #tonguetie #tonguetiebabies #breastfeedingsupport
...

Tag a friend who needs to hear this 💛 For many choices in parenting, there is no one right answer. We can use research and data to make informed decisions, but ultimately, it won’t tell you what to do. Only you can decide what will be best for your kids and your family.

I’m here to remind you to take a deep breath and trust yourself. I’ll be here to support you along the way. 

Thank you to everyone who submitted videos, including:
@sarah.consoli
@jess_lynn627
@nicolevandenwills
@thedrblair
@ncbenedict29
@haleycimini
@iamkellysnodgrass
@calesse_smith
@garnet__gordon
@jencoopgaiser87
@danigirl18c
@jamielundergreen
@carly_comber
@thecelebratingmama
@emilyannbynum
@eeliz413

#emilyoster #parentdata #parentingadvice #parentingsupport #parentingquotes

Tag a friend who needs to hear this 💛 For many choices in parenting, there is no one right answer. We can use research and data to make informed decisions, but ultimately, it won’t tell you what to do. Only you can decide what will be best for your kids and your family.

I’m here to remind you to take a deep breath and trust yourself. I’ll be here to support you along the way.

Thank you to everyone who submitted videos, including:
@sarah.consoli
@jess_lynn627
@nicolevandenwills
@thedrblair
@ncbenedict29
@haleycimini
@iamkellysnodgrass
@calesse_smith
@garnet__gordon
@jencoopgaiser87
@danigirl18c
@jamielundergreen
@carly_comber
@thecelebratingmama
@emilyannbynum
@eeliz413

#emilyoster #parentdata #parentingadvice #parentingsupport #parentingquotes
...

Congratulations on making it through another year of panic headlines! We’ve had some doozies this year, like aspartame causing cancer and the perils of white noise, but these headlines are very often based on poor data. Correlation does not equal causation. There will certainly be more panic headlines in 2024, but ParentData is here to debunk them for you.

#emilyoster #parentdata #happynewyear2024 #panicheadline #datadriven

Congratulations on making it through another year of panic headlines! We’ve had some doozies this year, like aspartame causing cancer and the perils of white noise, but these headlines are very often based on poor data. Correlation does not equal causation. There will certainly be more panic headlines in 2024, but ParentData is here to debunk them for you.

#emilyoster #parentdata #happynewyear2024 #panicheadline #datadriven
...