Throughout early modern history, Britain’s population changed at about the same speed as the rest of Europe. A really bad epidemic of the plague would drop the total numbers for a while, but on the whole there was a gradual increase, averaging less than one percent a year up until 1625, then remaining stable for 125 years, then increasing at a slow rate again to take 150 years to double.

Britain followed the pattern until the 1700s. In 1714, George 1, the first of the Hanoverians, came to rule over a country of 5.25 million. In 1760, the population had grown to 6.15 million, a healthy 17 percent at a time population growth in most of Europe was static. But the next 50 years would see a massive change. In 1815, the population was 10.25; almost double the 1714 figure. France in the same period saw a 35 percent increase, and the Dutch figures remained much the same.

Why did the population grow so fast?

Scholars give two reasons why Britain’s growth was faster than that of other nearby countries.

The first was a drop in mortality. Britain had more people because fewer of them died. From early in the eighteenth century, Britain began imposing quarantines on imports and ships sailing from places known to have the plague or other highly feared diseases. Innoculation against smallpox helped, too. People still died of typhus, cholera, and other diseases, but the number of deaths in each epidemic dropped dramatically.

The second was the age at marriage. Before the eighteenth century, the mainly agriculture-based workforce would put off getting married until they could afford a cottage and a small piece of land. Average age at marriage for women was 26 in the 17th century, and for men it was 28.  Fertility drops (on average) after 30, so not marrying until after 26 means fewer children overall.

The enclosure acts changed all that. The biggest landowners scooped up all the land, and people who would have been small-holders had to work for wages or migrate to the new jobs in city manufactories. Our working couples no longer had a reason to wait, so they married earlier and faced the challenges of finding work together. By the 19th century, the average age of marriage was 23 for women and 25 for men. (Not in the aristocracy. They married for different reasons, sometimes as young as 13 or 14.)

Since women now had a longer fertile period in marriage, and less chance of dying of disease, the number of children per couple increased.

In the next 150 years, decreasing infant and maternal mortality meant the British population doubled every 40 years, providing factory workers for industrial revolution and upsetting theorists like Malthus, who thought the upwards curve was the way things had always been, and that it would continue.