Numbers Don't Lie: 71 Stories to Help Us Understand the Modern World

by Vaclav Smil

The replacement level of fertility is that which maintains a population at a stable level. It is about 2.1, with the additional fraction needed to make up for girls who will not survive into fertile age.

In 1950, 40 percent of humanity lived in countries with fertilities above 6 and the mean rate was about 5; by the year 2000, just 5 percent of the global population was in countries with fertilities above 6, and the mean (2.6) was close to the replacement level. By 2050, nearly three-quarters of humanity will reside in countries with below-replacement fertility.

regional high fertilities guarantee that nearly 75 percent of all births during the 50 years between 2020 and 2070 will be in Africa.

So far, no pro-natalist government policies have brought any major reversal, and the only obvious option to prevent depopulation is to open the gates for immigration—but

Infant mortalities in preindustrial societies were uniformly and cruelly high: even by 1850 the rates in western Europe and in the United States were as high as 200–300 (that is, every fifth to every third child did not survive the first 365 days). By

A quadruped can take only a single breath per locomotive cycle, because its chest must absorb the impact on the front limbs. We, however, can choose other ratios, and that lets us use energy more flexibly.

in one hour, a horse can lose about 100 grams of water per square meter of skin, and a camel can lose up to 250 g/m2. However, a human being can easily shed 500 g/m2, enough to remove between 550 and 600 watts’ worth of heat.

In the race of life, we humans are neither the fastest nor the most efficient. But thanks to our sweating capability, we are certainly the most persistent.

And so, outside the microchip-dominated world, innovation simply does not obey Moore’s Law, proceeding at rates that are lower by an order of magnitude.

GDP is simply the total annual value of all goods and services transacted in a country. It rises not only when lives get better and economies progress but also when bad things happen to people or to the environment. Higher alcohol sales, more driving under the influence, more accidents, more emergency-room admissions, more injuries, more people in jail—GDP goes up.

100 grams of lean beef has 1.5 grams of saturated fat, compared with 1 gram in skinless chicken breast (which actually has more cholesterol).

warnings about the deleterious effect of consuming saturated dairy fat. That conclusion has been disproved, and the latest findings claim that dairy fat may actually lower the frequency of coronary heart disease and stroke mortality—but

Production of cement now accounts for about 5 percent of global CO2 emissions from fossil fuels,

mass and density are better indicators of sturdiness than of insulating capability.

Both in the United States and in the European Union, buildings account for about 40 percent of total primary energy consumption (transportation comes second, at 28 percent in the US and about 22 percent in the EU). Heating and air conditioning account for half of residential consumption, which is why the single best thing we could do for the energy budget is to keep the heat in (or out) with better insulation.

A single pane has a heat transfer coefficient of 5.7–6 watts per square meter per degree of kelvin; a double pane separated by 6 millimeters (air is a poor conductor of heat) has a coefficient of 3.3. Applying coatings to minimize the passage of ultraviolet and infrared radiation lowers it to between 1.8 and 2.2, and filling the space between the panes with argon (in order to slow down heat transfer) chops it to 1.1. Do that with triple-glazed windows and you drop to between 0.6 and 0.7. Substitute krypton for argon and you can get it down to 0.5.

Numbers may not lie, but which truth do they convey? In this book I have tried to show that we often have to look both deeper and wider. Even fairly reliable—indeed, even impeccably accurate—numbers need to be seen in wider contexts. An informed judging of absolute values requires some relative, comparative perspectives.

Rigid ranking based on minuscule differences misleads rather than informs. Rounding and approximation is superior to unwarranted and unnecessary precision.