Firecrackers explode in the sky over Delhi on the occasion of Diwali, October 24, 2022. Photo: PTI
- Delhi CM Arvind Kejriwal has said that the city is no longer among Asia’s top 10 cities with the most polluted air and called it ‘improvement’.
- His statement inadvertently highlighted the problems and pitfalls of using rank to measure progress, particularly through the lens of Goodhart’s law.
- India’s day-to-day politics incentivise our local as well as national ministers to goalify measures because they make attractive headlines and hide a deeper problem.
- As long as the quality of Delhi’s – and for that matter India’s – air remains beyond the WHO’s limit, whether the city is ranked #5, #50 or #100 won’t matter.
The Union finance minister Nirmala Sitharaman was lampooned over her attempt to defend the rupee’s weakening position against the US dollar – that the rupee wasn’t becoming weaker so much as the dollar was getting stronger. This is political palter but it’s also more than that: appeals to forces outside one’s jurisdiction is the typical response these days to problems about which the government won’t do anything, probably because it has spent a few years settling into a position wherefrom it can’t do anything.
Delhi chief minister Arvind Kejriwal demonstrated this as well as Sitharaman did when he said recently that New Delhi is no longer among Asia’s top 10 cities with the most polluted air, called it ‘improvement’ and added that the city still has a long way to go. That is, Delhi is no longer the most polluted because other cities are more polluted. The first his claims may be true, the third is definitely true, but the second is not.
Reuters reported that on October 24, residents of the national capital defied the city government’s firecracker ban, causing the hourly average concentration of PM2.5 particles to soar to a horrific 700 µg/m3 at 2 am on October 25. This value is more than 10-times India’s self-prescribed limit and nearly 30-times the WHO’s recommendation. But just a single day isn’t the problem – or it would be if New Delhi’s ‘airpocalypse’ was the product of a single cause. The problem is that the crisis as it persists today is entirely of socio-political making, which makes it messy and, importantly, vulnerable to being subsumed by Goodhart’s law: that “any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes”.
Kejriwal’s statement is guilty of this because it transforms a measure (Delhi’s rank on a list of cities with the worst air quality) into a goal (“Delhi is no longer in the top 10, so the air has improved”). According to the law, when a measure becomes a goal, it stops being a measure. There are of course two ways to interpret his statement, but which also highlight a big risk in the fray: that this is the chief minister of a Union territory where air pollution can make or break political careers scoring points as and when he can to stay ahead of his opponents’ accusations of inaction, or that this is an admission that his government was targeting not reducing pollution per se but getting out of the top 10 by rank.
The risk is that India’s day-to-day politics incentivise our local as well as national ministers to goalify measures, because they make attractive headlines while hiding a deeper problem. When a measure becomes a goal, the benchmark for the measure will no longer move. That is, if the Delhi government – national or local – aimed to move the city out of the top 10, the city could be at #11 but still have the same PM2.5 concentration it did last year. This is possible when 10 cities join the list at the top because, say, they have recently started industrial activity en masse that pollutes the air much more than Delhi does.
Instead, if Delhi’s position on the air-quality ranking remained a measure, it would be one of many boxes for the government to tick and, once ticked, the government could move on to the next one. For example, now that the Kejriwal government has moved Delhi out of the top 10, it can retrain its focus on the ultimate goal: the WHO’s recommended outdoor PM2.5 concentration of 25 µg/m3 (24-hour average).
According to UrbanEmissions, between 2014 and 2016, the PM2.5 concentration over Delhi increased by around 10% (see infographic below). The average annual PM2.5 concentration was roughly uniform in the four years from 2016 to 2019, around 120 µg/m3. It dipped in 2020, likely due to the COVID-19 lockdown. In an April 2020 analysis, Sarath Guttikunda, founder of UrbanEmissions, found that the average PM2.5 concentration in 2017-2019 for March was 100-140 µg/m3 but which in 2020 was just 35 µg/m3. The annual average concentration for the year was 84 µg/m3. In 2021, according to PTI, this figure was 96.4 µg/m3. So as things stand, particulate pollution is becoming worse again – even as it remains far beyond the WHO’s recommended limit.
Recall that the WHO revised the “acceptable” annual mean concentration of outdoor PM2.5 from 10 µg/m3 to 5 µg/m3 in 2021. Effectively, Delhi exiting the top 10 in the list of Asia’s cities with the foulest air counts for… nothing. This brings us to the other advantage of focusing on the WHO’s limit as the goal is that reducing the pollution will also improve health outcomes. Scientists have associated PM2.5 in the outdoors with heart and respiratory diseases, higher cancer risk (even among non-smokers), “lost pregnancies” and shorter lifespans. The WHO has also noted that there is no minimum threshold at which PM2.5 ‘becomes’ deleterious; it is bad for health at all concentrations.
That is, as long as the quality of Delhi’s – and for that matter India’s – air remains beyond the WHO’s limit, whether the city is ranked #5, #10 or #100 won’t matter. So one hopes – especially during the festival of foul-air – that our local and national governments will focus on the real problem.