Over the last century there was a remarkable decline in deaths due to hot days and heatwaves. (Not that the media seem keen to say so). Mortality on a hot day declined by fully 75% in the decades after 1960 when air conditioners started to be rolled out.
In the words of the authors from this 2016 study, the people of the US have largely adapted in ways that protect them from extreme heat. The kind of hot days they are talking about happen on average 20 days a year in the US.
There has not been a similar reduction in deaths from cold snaps.
First, we document a remarkable decline in the mortality effect of temperature extremes: The impact of days with a mean temperature exceeding 80°F (26.6C) has declined by about 75 percent over the course of the twentieth century in the United States, with almost the entire decline occurring after 1960. The result is that there are about 20,000 fewer fatalities annually than if the pre-1960 impacts of mortality still prevailed.
We achieved a lot of things in the 20th century, but when Barreca went through the statistics, it wasn’t the introduction of electricity that prevented most deaths — even though it brought fridges, and water, and fans — almost the entire effect was due to air conditioners. The researchers also considered health care access with doctors per capita, but that didn’t do it either.
In terms of money — Air conditioners add about 11% to the average household’s electricity bill, but in the long run save money.
“The present value of US consumer surplus from the introduction of residential AC in 1960, which is the first year in which we measure the AC penetration rate, ranges from $85 to $185 billion (2012 dollars) with a 5 percent discount rate.
Apparently most of the money saved comes from “avoided deaths” — and an economist might need to explain to me what that really translates into. In the 2015 version they admit there are a lot of benefits and costs that are not included — like improvements to worker productivity, or increases in pollution.
The paper is freely available. It’s an interesting history of mortality and technology in the last hundred years.
The graphs of how temperature affects the mortality rate
a/ 1904-2004 b/ 1931-2004 Click to enlarge
The big difference shows when the data is divided into pre 1960 (c) and post 1960 (d) curves below. Then the increase in mortality for hotter days is more obvious.
c/ 1931-1959 d/ 1960 – 2004 | Click to enlarge
If we want to save the poor in Africa from dying of heat waves, the best thing we can do is help them get air conditioning and the cheap electricity to run it.
Abstract
This paper examines the temperature-mortality relationship over the course of the twentieth-century United States both for its own interest and to identify potentially useful adaptations for coming decades. There are three primary findings.
First, the mortality impact of days with mean temperature exceeding 80°F declined by 75 percent. Almost the entire decline occurred after 1960. Second, the diffusion of residential air conditioning explains essentially the entire decline in hot day–related fatalities. Third, using Dubin and McFadden’s discrete-continuous model, the present value of US consumer surplus from the introduction of residential air conditioning is estimated to be $85–$185 billion (2012 dollars).
This paper provides the first large-scale empirical evidence on long-run adaptation opportunities through changes in the use of currently existing technologies. The empirical analysis is divided into three parts. The first part documents a remarkable decline in the mortality effect of temperature extremes: the impact of days with a mean temperature exceeding 80°F has declined by about 75 percent over the course of the twentieth century in the United States, with almost the entire decline occurring after 1960. The result is that there are about 20,000 fewer fatalities annually than if the pre-1960 impacts of mortality still prevailed. At the same time, the mortality effect of cold temperatures declined by a substantially smaller amount. In effect, US residents adapted in ways that leave them largely protected from extreme heat.
The second part of the analysis aims to uncover the adaptations that muted the relationship between mortality and high temperatures. We focus attention on the spread of three health-related innovations in the twentieth-century United States: residential electricity, access to health care, and residential air conditioning (AC). There are good reasons to believe that these innovations mitigated the health consequences of hot temperatures (in addition to providing other services). Electrification enabled a wide variety of innovations including fans, refrigeration, and later air conditioning. Increased access to health care allowed both preventative treatment and emergency intervention (e.g., intravenous administration of fluids in response to dehydration; see Almond, Chay, and Greenstone 2006). Air conditioning made it possible to reduce the stress on people’s thermoregulatory systems during periods of extreme heat.
The third part of the analysis develops a measure of the full consumer surplus associated with residential AC, based on the application of Dubin and McFadden’s (1984) discrete-continuous model. This analysis is conducted with household-level census data on AC penetration rates and electricity consumption, as well as data on electricity prices. We find that AC adoption increases average household electricity consumption by about 1,000 kilowatt-hours (kWh) or 11 percent. We estimate that the gain in consumer surplus associated with the adoption of residential AC ranged from about $5 to $10 billion (2012 dollars) annually at the 1980 AC penetration rate, depending on the assumptions about the shape of the long-run electricity supply curve. This translates into an increase in consumer surplus per US household in 1980 of $112–$225. The present value of US consumer surplus from the introduction of residential AC in 1960, which is the first year in which we measure the AC penetration rate, ranges from $85 to $185 billion (2012 dollars) with a 5 percent discount rate.
It wasn’t electricity, fans, fridges or doctors that saved people from heat, it was air conditioners
We focus attention on the spread of three health-related innovations in the twentieth-century United States: residential electricity, access to health care, and residential air conditioning (AC). There are good reasons to believe that these innovations mitigated the health consequences of hot temperatures (in addition to providing other services). Electrification enabled a wide variety of innovations including fans, refrigeration, and later air conditioning. Increased access to health care allowed both preventative treatment and emergency intervention (e.g., intravenous administration of fluids in response to dehydration; see Almond, Chay, and Greenstone 2006). Air conditioning made it possible to reduce the stress on people’s thermoregulatory systems during periods of extreme heat. The empirical results point to air conditioning as a central determinant of the reduction of the mortality risk associated with high temperatures during the twentieth century. Specifically, the diffusion of residential AC after 1960 is related to a statistically significant and economically meaningful reduction in the temperature-mortality relationship at high temperatures. Indeed, the adoption of residential air conditioning explains essentially the entire decline in the relationship between mortality and days with an average temperature exceeding 807F. In contrast, we find that electrification (represented by residential electrification) and access to health care (represented by doctors per capita) are not statistically related to reductions in heat-related mortality
REFERENCE
Alan Barreca, Karen Clay, Olivier Deschenes, Michael Greenstone, and Joseph S. Shapiro (2016) Adapting to Climate Change: The Remarkable Decline in the US Temperature-Mortality Relationship over the Twentieth Century, Journal of Political Economy 124:1, 105-159 [Berkley PDF]
A working paper with the same title and authors was issued in 2013 by the NBER