The chief executive of the Public Religion Research Institute and a digital columnist for The Atlantic, Jones has dug through mountains of surveys and polls. The result is what he frankly calls an “obituary” of the nation’s shrinking population of white Protestants. The data are eye-popping. In 1993, the year Bill Clinton took office, a healthy 51 percent of Americans “identified as white Protestants.” In 2014, “that percentage dropped to 32,” Jones reports. And the news keeps getting grimmer, as millennials stream for the church exit, turned off by intolerant “anti-gay teachings” thundered forth from evangelical pulpits.

Since 1952, no Democratic presidential candidate has won college-educated whites.

[T]he most striking historical trend of Elizabeth II’s reign has been a sudden ethnic transformation of Britain. In 1931, when the queen was a child of 5, only 1.75 percent of Britain’s population was foreign-born. Her rule saw the Empire come to Britain: For the first time, the island experienced large-scale nonwhite immigration from Asia, Africa and the Caribbean. By 2011, when she was 85, about 20 percent of the population of England and Wales were immigrants or the children of immigrants.

When the queen celebrated her 90th birthday this year, more than 12 percent of her subjects were nonwhite. This is the new England, but London is already another country. In 1971, 86 percent of Londoners were still white British. Forty years later, fewer than half were. Urban areas with a population less than 60 percent white British now include such major cities as Slough, Leicester, Luton and Birmingham. Ethnic change is gathering pace: By 2050, roughly 30 percent of Britons could be nonwhite.

At the end of World War II, 11 percent of students nationwide chose to major in the humanities. In the 1960s, this figure rose to 17 percent, but now it stands at around 6 percent. Students are increasingly drawn to vocational majors in subjects like business, medicine, science, and education.

The pound fell to £1 to US$1.28 in the two weeks after the Brexit result. This has only been reached once in all the time these two currencies have existed – for a two-year period in the 1980s. And in the 1980s, the low rate was not due to a fundamentally weak pound, but to a strong dollar. All European currencies at the time fell against the dollar and were saved in 1985 by the Plaza Accord, a commitment by the US and Europe’s major economies to support their currencies through market intervention.

Apart from this brief episode between 1984 and 1985, sterling is now at its lowest against the US dollar since 1792, when the first American dollar was minted. The morning after the announcement of the Brexit result on June 24, sterling had dropped 10% overnight and was down 8% at the end of the trading day. Only four times since 1900 did the pound drop so much in one day – in 1931, 1940, 1949 and 1967. Two of these four falls were government induced devaluations.

In all, the top 1 percent in the United States captured 85.1 percent of total income growth from 2009 to 2013. In 2013, the 1.6 million families in the top 1 percent made 25.3 times as much on average as the 161 million families in the bottom 99 percent.

Those and other figures are reminiscent of conditions in the Roaring Twenties. In 1928, the peak year of that decade’s boom, the top 1 percent took home 24 percent of the nation’s income. In 2013, the top 1 percent nationally took home 20.1 percent of all income, while in five states (New York, Connecticut, Wyoming, Nevada and Florida) the income share for the top 1 percent exceeded the peak from 1928.

More than 18 million Asian-Americans live in the United States, more than 5.5 percent of the population. Chinese comprise the largest group, more than 4 million, followed by Filipinos, Indians, Vietnamese, Koreans and Japanese. They are the fastest-growing ethnic minority and are expected to play an increasingly important role in elections.

There are about 100,000 Jews who were in camps, ghettos and in hiding under Nazi occupation who are still alive today, according to the Conference on Jewish Material Claims Against Germany, one of the few international organizations that tracks that type of data. The group, which negotiates with Germany’s government for payments to Holocaust victims and provides social services for survivors, said there were about 500,000 living survivors, including those who fled Nazi Germany, in 2014.

On the off chance he actually is planning to back out, what would happen?

Alexander Keyssar, a historian at Harvard who is working on a book about the Electoral College, said the process of succession would depend on “the precise moment at which he said, ‘Nah, never mind.’”

The party representatives who make up the Electoral College would suddenly have real power rather than a rubber stamp. If Mr. Trump bowed out after winning on Nov. 8 but before the electors met in each state to cast their ballots on Dec. 19, then the electors could have the opportunity to vote for another candidate, Professor Keyssar said.

A majority of the 538 electors would be Republicans, but they might not agree on the best alternative candidate. If no one won a majority of the electors, the contest between the top three vote-getters — one of whom would presumably be Mrs. Clinton — would go to the House of Representatives, where each state would be given one vote, while the Senate would select the vice president. House Republicans hold 33 states to the Democrats’ 14, with three evenly split. It is unclear whether the vote would take place before or after newly elected representatives were seated.

It is also unclear what would happen, Professor Keyssar said, if Mr. Trump bid adieu after the electoral votes were cast but before they were officially counted, per the 12th Amendment, by the president of the Senate before a joint session of Congress in January. And if Mr. Trump left after the votes were counted in Congress but before he was sworn in on Jan. 20, Professor Keyssar said the closest guidance would probably come from Section Three of the 20th Amendment: “If, at the time fixed for the beginning of the term of the president, the president-elect shall have died, the vice president-elect shall become president.”

“Nothing like this has ever happened,” Professor Keyssar said.