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Drew Johnston Profile
Drew Johnston

@drew_m_johnston

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Economics PhD candidate @harvard . I like computers, cities, and social influence.

Joined November 2018
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@drew_m_johnston
Drew Johnston
3 years
I'm excited to announce the release of the zip code Social Connectedness Index! It captures the rate of Facebook friendships between zip codes. This data set allows for much more granular uses than before. A 🧵 of examples:
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@drew_m_johnston
Drew Johnston
5 months
Dissertation defended! I'm excited to announce I'll be coming on as a postdoc at Meta to keep working on a few projects I'm pretty excited about--stay tuned!
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@drew_m_johnston
Drew Johnston
3 years
But there are certainly more stories left to be told using this data, so download it for yourself and play around in your favorite statistical software. A number of other granularities (US and international) are available if zip codes aren't what you need.
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@drew_m_johnston
Drew Johnston
3 years
There's a ton more in here. It's possible to see that friendships tend to coincide with public transit lines (), and possible to see that there's a ton of variation in how clustered areas' social networks are.
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@drew_m_johnston
Drew Johnston
3 years
There are a lot of micro stories in the zip code social connectedness data--for instance, the areas in the Bay Area most connected to 08540 (Princeton NJ) are home to research universities. (Check my pinned thread for a link to the data!)
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@drew_m_johnston
Drew Johnston
3 years
It's possible to dive more deeply than before into the connections of specific neighborhoods. For instance, you can see that Flushing (home of the best Chinese food in NYC) is closely connected to NYC's other Chinatowns, in Brooklyn and Manhattan.
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@drew_m_johnston
Drew Johnston
3 years
It's possible to see how sharply connections fall along class lines as well--compare the social networks of the neighboring zips 11218 (the ritzy Upper East Side) and 10029 (East Harlem) ...this one is so stark that the NYT wrote an article about it ()
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@drew_m_johnston
Drew Johnston
3 years
@MelissaLDell This is amazing and I wish this had been around five years ago! I spent a lot of time doing this by hand for my first RA job :)
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@drew_m_johnston
Drew Johnston
3 years
You can also dive deep into the connections between neighborhoods ACROSS cities--for instance, you can map connections between Flushing and the Boston metro, and see that a number of areas with large Chinese populations pop out.
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@drew_m_johnston
Drew Johnston
2 years
I'm very happy to see the culmination of our team's research out today! Check out the data visualization in the NYT as well:
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@drew_m_johnston
Drew Johnston
3 years
Huge thanks to @michaelcbailey , @stroebel_econ , @DomRussel , Theresa Kuchler, Pat Farrell, and Alex Pompe for making this possible.
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@drew_m_johnston
Drew Johnston
3 years
Let us know if you find anything interesting using this data!
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@drew_m_johnston
Drew Johnston
2 years
We're also making aggregated data on social capital at the HS/college/zip code/county level here:
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@drew_m_johnston
Drew Johnston
3 years
Link to the data:
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@drew_m_johnston
Drew Johnston
2 years
@avi_collis @stroebel_econ @michaelcbailey @DomRussel Looking at how the results generalize to other migrant groups/countries would definitely be interesting! With earlier migrants we don't observe migration time though, which rules out some of the analyses. Other countries would be cool tool, though some inst. knowledge is needed!
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@drew_m_johnston
Drew Johnston
2 years
@stephkestelman @RFisman @Harvard @Princeton @Columbia You would not BELIEVE how useful sword fighting is in the world of econ research
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@drew_m_johnston
Drew Johnston
4 years
@PopulismUpdates You might be right--this website says 18 for local government positions, but doesn't seem to be mentioned in the charter.
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@drew_m_johnston
Drew Johnston
2 years
@paula_slspi @CarolinPflueger @stroebel_econ @Ogoun I think just because this project is old! If I remember correctly, when we started working on this project ivreghdfe was new and did not let you cache residuals between regressions. This was 5 years ago though so my memory might be hazy. Big picture, feel free to use ivreghdfe--
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@drew_m_johnston
Drew Johnston
3 years
@ChrisTokita Check out page 16 of the working paper I linked to in the thread!
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@drew_m_johnston
Drew Johnston
5 years
@MarketUrbanism Might make a difference for low-income renters if the fee is paid upfront vs factored into the rent over time
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@drew_m_johnston
Drew Johnston
2 years
@stephkestelman @RFisman @Harvard @Princeton @Columbia The NCAA fencing -> econ PhD pipeline is shockingly strong... the causality is a bit murky though :p
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@drew_m_johnston
Drew Johnston
2 years
@paula_slspi @CarolinPflueger @stroebel_econ @Ogoun not sure why they give slightly different answers, but I think ivreghdfe is better maintained these days (we had to set a flag called "old" to get our legacy code to keep working with reghdfe)
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@drew_m_johnston
Drew Johnston
2 years
@CarolinPflueger @paula_slspi @stroebel_econ @Ogoun We used this code in the Peer Effects in Product Adoption paper--you can check it out in context in our replication package (). I never really intended for it to be used more widely, but hopefully it solves your problem!
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@drew_m_johnston
Drew Johnston
4 years
@ben_golub Pricing in markets with more options seems wackier than in markets with fewer--I'd imagine it's a function of PredictIt charging you a 10% charge on gross (not net) profits in each market, so you can't short everything easily.
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@drew_m_johnston
Drew Johnston
3 years
@WillRinehart County is already available at the link! Other granularities as well.
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@drew_m_johnston
Drew Johnston
3 years
@aleszubajak This is an updated version of the data, using connections from this month! Not sure I'm allowed to share a user number.
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@drew_m_johnston
Drew Johnston
4 years
Seems plausible that decking could be a better solution for BQE in Williamsburg, Prospect Expressway... Would add housing and still leave room for biking/walking infrastructure
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@drew_m_johnston
Drew Johnston
3 years
@AbbiasovTimur @PPS_Placemaking @NYCParks Awesome paper! Glad to see this data being used :)
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@drew_m_johnston
Drew Johnston
3 years
@fvigeland Finn, this is incredible!!
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@drew_m_johnston
Drew Johnston
4 years
@2AvSagas No Revel after midnight either!
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@drew_m_johnston
Drew Johnston
3 years
@lara_putnam @urbanclio @PrdctblyIrrtnl (We then re-scale the values to mask user counts, but this is the basic intuition)
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@drew_m_johnston
Drew Johnston
4 years
This is awesome, hopefully a sign of a bigger shift in thinking. I wonder if funding will be available for decking over highways too... Boulevards are nice in a lot of cases, but in others decking could add land for housing/parks/whatever instead of a still-wide street...
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@drew_m_johnston
Drew Johnston
3 years
@pedrosaffi Nope, there are a bunch of other granularities available at the link!
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@drew_m_johnston
Drew Johnston
3 years
@lara_putnam @urbanclio @PrdctblyIrrtnl Between two places with 10 pop, there are 100 friendships if everyone is connected (the numerator). So the SCI if all friendships are formed is 100 / (10*10) = 1. Between two places with 100 pop, there are 10k possible friendships, so the SCI if fully connected is 10k/(100*100)=1
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@drew_m_johnston
Drew Johnston
3 years
@TBroekel Sure thing! We don't currently have zip-level data for Europe but on the site where the data is distributed we also have something at the NUTS3 level.
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@drew_m_johnston
Drew Johnston
5 years
@andrewsalzberg Any plans to make public the materials from your winter session class?
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@drew_m_johnston
Drew Johnston
2 years
@IAmWilbur those are very competitive i'm not sure
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@drew_m_johnston
Drew Johnston
3 years
@lara_putnam @urbanclio @PrdctblyIrrtnl The denominator self-sci is n^2-n (since friendships ARE counted both ways for self sci)
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