The latest project out of MIT's Senseable City Lab examines the "sensing power of taxis" in various cities around the world. Looking at traffic data, they determined how many circulating taxis you would need to equip with sensors if you wanted to capture comprehensive street data across a particular city. This might be useful if you wanted to measure things like air quality, weather, traffic patterns, road quality, and so on.

What they found is that the sensing power of taxis starts out unexpectedly high. It would only take 10 taxis to cover 1/3 of Manhattan's streets in a single day. However, because taxis tend to have convergent routes, they also discovered rapid diminishing returns. It would take 30 taxis (or 0.3% of all taxi trips) to cover half of Manhattan in a day, and over 1,000 taxis to cover 85% of it. A similar phenomenon was observed in the other cities that they studied: Singapore, Chicago, San Francisco, Vienna, and Shanghai.

However, if you look at the percentage of trips needed to scan half of the streets in a city, Manhattan has the lowest rate at 0.3%. Vienna is the highest at 9%. But I'm not sure if this is a function of the utilization rate of their taxis or if it has something to do with urban form. Singapore has a similarly low rate (0.44%), but its street grid looks nothing like that of New York's.

Here's a short video explaining the project:

Below is a list of the 44 cities found in the 2018 Global Power City Index by the Mori Memorial Foundation's Institute for Urban Strategies.

The index ranks the major cities of the world according to their "magnetism", which they generally define as a city's ability to attract people, capital, and businesses from around the world.

As with all rankings, the output depends entirely on the methodology that you use. The GPCI seems to have the right executive committee in place. It includes global city authorities like Saskia Sassen. But that's not really the point of today's post.

Beside each city, I have added the average highs and lows (in celsius) for both the coldest and hottest months of the year. For cities in the northern hemisphere, these are typically January and July/August, respectively.

I have also added the spread between the hottest and coldest months to get a sense of variability. I always find it interesting to see how cities like Singapore, Kuala Lumpur, Jakarta, and Mumbai basically stay the same temperature all year round.

When you look at this list, remember that you can ski in Dubai.

All weather data taken from the NOAA (National Oceanic and Atmospheric Administration).

In Edward Glaeser’s book, Triumph of the City, he argues that the average temperature in January is the single best variable to predict which U.S. cities have grown the most over the last century. Indeed, from July 2015 to July 2016, 10 of the 15 fastest growing large metro areas in the U.S. were in the south. Follow the sun and sprawl.

Given this phenomenon, I thought it would be interesting to look at the world’s most influential cities (i.e. global cities) through this lens. Because let’s face it, New York and London aren’t all that warm in January. 

Below are the top 25 global cities (taken from A.T. Kearney’s 2018 Global Cities Report), along with their average January temperature (taken from here). Note, there are two rankings. On the left is their global cities index. And on the right is their global cities outlook, which evaluates current potential. Cities that improved their economics & governance made the biggest leap on the right.

First of all, it’s interesting to see San Francisco jump so significantly in their outlook ranking. This has everything to do with tech and innovation. It’s also important to note that a handful of the above cities are located in the southern hemisphere, so “average January temperature” doesn’t mean the same thing (probably should have normalized to their winter).

Montreal wins the award for the coldest city in this ranking. And there’s really only one city, Singapore, with a tropical climate. Though there are others, such as Hong Kong and Sydney, that would fall under subtropical. All of this isn’t enough for us to start inferring anything, but perhaps colder and more temperate climates aren’t such a bad thing for economic growth.