Past research has shown that as cities get larger, people tend to walk faster. The probable explanation for this is that as cities get bigger, they also tend to get wealthier, and so the opportunity cost of not walking fast increases. In other words, people's time is worth more.

Of course, there's something naturally unsettling about this. But it appears to be demonstrably true. Here's another, more recent, study that compares pedestrian behavior in 1979-1980 to 2008-2010 for four urban public spaces in New York, Boston, and Philadelphia.

What the researchers did was use William Whyte's famous observational work from 1980 and then use computer vision to compare it to 2008-2010. And what they found was that, on average, walking speeds had increased by about 15% and that time spent lingering in these public spaces had basically halved across all locations.

These are pretty dramatic changes that speak to a different, or at least, evolving, urban life. Increasingly, we're all just atoms racing around and trying to get to our next engagement.

Now, part of this can likely be attributed to the greater opportunity cost thing. But another possible explanation might be the advent of the internet and smartphones. Could this be a symptom of our social lives moving away from our streets and being replaced by online platforms?

A friend recently asked me, "so, are you bullish on Miami yet, or are you still worried about the water?" And my response was that I love Miami, but that I do think about the risk of climate change.

Then today, another friend sent me this study by scientists at the University of Miami showing that 35 buildings along the Miami Beach to Sunny Isles Beach coastline experienced some degree of subsidence between 2016 to 2023. In other words, they sunk into the ground a little.

Here's how they measured this:

The study published December 13, 2024, in the open-access journal Earth and Space Science, of the American Geophysical Union, employed a satellite-based technique known as Interferometric Synthetic Aperture Radar (InSAR). By combining 222 SAR images from the European Sentinel-1 satellites, the research team created a surface displacement time series. The technique utilizes "persistent radar scatterers" as reference points for measurement. These scatterers include fixed elements on a structure such as building balconies, rooftop air conditioning units, and boardwalks, which reflect the radar signal back to the satellite antenna. Satellites flying at 700 kilometers above Earth can measure millimeter-scale displacements.

Now, some degree of subsidence is normal. But apparently, not this much:

“The discovery of the extent of subsidence hotspots along the South Florida coastline was unexpected,” said Farzaneh Aziz Zanjani, the study’s lead author, a former post-doctoral researcher and alumna of the Rosenstiel School. “The study underscores the need for ongoing monitoring and a deeper understanding of the long-term implications for these structures.”

So yeah, I'm still worried about the water. It's something I would need to get a lot smarter on in order to feel comfortable.

Paris is the first city in France to implement some form of residential rent control. The first came in 2014 (enacted in the market in 2015), but this was later removed in 2017. The second came in 2019, and this current program remains in place until November 2026, at which time it will be reviewed.

But given that it has already been in place for a number of years, people have started to analyze it's effectiveness. Here is a study by Atelier Parisien d'Urbanisme (APUR) that was published this month.

The report is in French, but I can tell you that, what they did, was compare the Paris region to 8 other cities in France -- all of which do not have the same rent controls. They were: Aix-en-Provence, Grenoble, Marseille, Nantes, Nice, Strasbourg, Toulon, et Toulouse. These were allegedly chosen because their housing markets are thought to be similar to that of Paris'.

What they found was that from July 2019 to July 2023, legislated controls in Paris lowered rents by approximately 4.2%, compared to where they would have been without any market intervention.

At the same time, they noticed that these same controls seemed to become more effective over time. From July 2019 to June 2020, they lowered rents by 2.5%, but from July 2022 to June 2023, they lowered rents by 5.9%.

Finally, they also found that the controls seemed to impact smaller places the most. For apartments between 8 and 18 m2, rents were 10.2% lower than expected during July 2019 and July 2023.

This is all interesting stuff, but in many ways, it is expected. Rent controls are intended to depress rental growth. That's the whole point. And based on this data from APUR, it is working in Paris.

But the really tough questions pertain to the possible knock-on effects. If rents are 4.2% lower, but operating costs are now growing faster than rents, then this is a problem for the housing market. You're on an unsustainable path.

And if lower rents mean that fewer developers are going to build new housing, then this is also a problem, because less supply will eventually translate into more upward pressure on rents. I don't know for sure that this is happening in Paris, right now, but these are crucial considerations.

It's never as simple as just looking at rents and thinking lower is better for long-term affordability.