Did you know that the incidence of cancer in the United States has been declining for nearly 20 years? That the spread of pornography correlates with a decline in rape? That average IQs are going up substantially all around the world? These are just some of the truths that are well-known to the scholars who study those subjects but generally come as a surprise to even the best-educated among us.

As reason reflects on how the world has changed since the magazine's founding in May 1968, here are seven surprising pieces of unalloyed good news.

Cancer Rates Are Going Down

A 2007 American Cancer Society poll found that seven out of 10 Americans believed that the risk of dying from cancer is going up. In fact, not only have cancer death rates been declining steeply, age-adjusted cancer incidence rates have been falling for nearly two decades. That is, in nearly any age group, fewer Americans are actually coming down with cancer.

Advances in modern medicine have increased the five-year survival rates of cancer patients from 50 percent in the 1970s to 68 percent today. That much you might expect. More surprising is that the incidence of cancer has been falling about 0.6 percent per year since 1994. That may not sound like much, but as John Seffrin, CEO of the American Cancer Society, explains, "in recent years, about 100,000 people each year who would have died had cancer rates not declined are living to celebrate another birthday."

Why is cancer becoming more rare? Largely because fewer Americans are smoking, more are having colonoscopies in which polyps that might become cancerous are removed, and many women stopped hormone replacement therapy in the early 2000s, all behaviors that prevent the onset of cancer. Advances in genetic screening for cancer risks will further reduce cancer incidence as empowered patients take preventive actions like actress Angelina Jolie's double mastectomy, which reduced her lifetime risk of heritable breast cancer from around 90 percent to 5 percent.

The news is not all good. Rising levels of obesity have been associated with increases in cancers of the kidneys, esophagus, pancreas, and elsewhere. But falling mortality and incidence rates do indicate real progress in the War on Cancer.

More Porn, Less Rape

Over the past two decades, as pornography has become much more easily accessible over the Internet, the rate of rape and sexual assault has declined by about 60 percent, according to the Department of Justice's Bureau of Justice Statistics (BJS).

The BJS conducts an annual National Crime Victimization survey of more than 100,000 households, asking if anyone has been the victim of various crimes in the past year. In 1995, the rape/sexual assault rate was reported as 5 per 1,000 American women over age 12. In 2011, the rate had fallen to 1.8 rapes/sexual assaults per 1,000.

Meanwhile access to pornography has dramatically increased. "It is a truth universally acknowledged, that a person in possession of a fast Internet connection must be in want of some porn," the journalist Sebastian Anthony joked last year on the website Extremetech. Dozens of porn platforms are among the top 500 sites in terms of traffic, according to Google's Doubleclick Ad Planner. The largest, Xvideos, draws 4.4 billion page views per month—three times more than CNN or ESPN, and twice as many as Reddit.

A comprehensive 2009 review in the journal Aggression and Violent Behavior by the Texas A&M International University psychologist Christopher Ferguson and the University of Texas at San Antonio criminologist Richard Hartley concluded that easy access to porn does not cause rape. "Considered together, the available data about pornography consumption and rape rates in the United States seem to rule out a causal relationship," Ferguson and Hartley wrote in their summary of the academic literature. "One could even argue that the available research and self-reported and official statistics might provide evidence for the reverse effect; the increasing availability of pornography appears to be associated with a decline in rape."

The Clemson economist Todd Kendall, in a 2006 study supported by the National Bureau of Economic Research, concluded that "Internet access appears to be a substitute for rape; in particular, the results suggest that a 10 percentage point increase in internet access is associated with a decline in reported rape victimization of around 7.3 percent." Kendall found that "there is no statistically significant relationship between internet access and any individual FBI index crime (other than rape), including murder, robbery, aggravated assault, robbery, larceny, and auto theft." Crime rates are plummeting all over, but it's only rape that appears to be pegged to online connectivity.

Longer Life Expectancy Stops Population Growth

An exciting convergence between demography and evolutionary theory is shedding considerable light on why people the world over are having fewer children. It turns out that the longer people can expect to live, the fewer children they have. In fact, if current fertility trends continue, world population could well top out in the middle of this century at between 8 and 9 billion, then begin to decline.

A fascinating study by the University of Connecticut anthropologists Nicola Bulled and Richard Sosis looks at life expectancy and fertility rates in 193 countries. In the October 2010 issue of Human Nature, they report that "when life expectancy is high, educational attainment is also high, reproductive timing is delayed, and overall reproduction reduced."

The University of Michigan ecologist Bobbi Low and her colleagues have found that once women can expect to live past age 60, they begin to have their first child later in life and have fewer children overall. Longer life expectancy is also correlated with more education for women.

Bulled and Sosis report a similar finding: Women who live in countries where life expectancy is below 50 years bear an average of 5.5 children. When life expectancy is between 50 and 60, they bear an average of 4.8 children. The big drop occurs when they can expect to live between 60 and 70 years, in which case women have about 2.5 children on average. The decline continues if women expect to live between 70 and 75 years to 2.2 children, and falls to just 1.75 children if they can expect to live older than 75.

The United Nations World Population Prospects 2010 Revision reported that world average life expectancy for women is now 70 years. Global average life expectancy in 1960 was 52 years and the total fertility rate was about 5 children per woman. As life expectancy keeps rising, average total fertility today has fallen to a world average of 2.36 children per woman, just slightly above the 2.1 replacement rate.

People Everywhere Are Getting Smarter

About half of Americans two generations ago would have been diagnosed as mentally retarded based on today's IQ tests.

In 1980, the New Zealand political scientist James Flynn discovered that average IQs in many countries have been drifting upward at about 3 points per decade over the past couple of generations. In fact, the average has risen by an astonishing 15 points in the last 50 years in the United States. In other words, a person with an average IQ of 100 today would score 115 on a 1950s IQ test, and a person of average IQ today would have been in approximately the top 15 percent of same-age scorers 50 years ago. If the average American kid were to take the first Stanford-Binet IQ test from 1932, she would score about 124 points today.

"This means that on an IQ test made in 1930 the average score of the entire population would give an IQ between 120 and 130 according to the original standardization," the Hungarian technologist Kristóf Kovács explains. So "instead of 2 percent, 35–50 percent of the population would have an IQ above 130. And vice versa; if the current standard was applied to people living in 1930, average IQ would be between 70 and 80, and instead of 2 percent, 35–50 percent would be diagnosed with mental retardation."

What accounts for this massive increase in IQ scores? Researchers have suggested a panoply of causes, including better nutrition, exposure to more mentally challenging media, and more formal schooling, but my favorite is the reduced load of infectious childhood diseases.

A fascinating study published in the June 2010 Proceedings of the Royal Society by the University of New Mexico biologist Christopher Eppig and his colleagues finds an intriguing correlation between the average IQ of a country's citizens and the intensity with which they suffer from parasites and infectious diseases. The authors note that the brains of newborns burn up 87 percent of infants' metabolic energy; 5-year-old brains use 44 percent; and adult brains consume 25 percent of the body's energy. Mobilizing the immune system to fight off diseases and parasites is very metabolically expensive, diverting nutrients and energy that would otherwise be used to fuel the building and maintenance of the human brain. If this analysis is substantially correct, then promoting public health also promotes higher IQs.

The new study reports, "Infectious disease remains the most powerful predictor of average national IQ when temperature, distance from Africa, gross domestic product per capita and several measures of education are controlled for. These findings suggest that the Flynn effect may be caused in part by the decrease in the intensity of infectious diseases as nations develop."

The converse of this research should find a correlation between higher average IQs and increasing allergy and asthma rates. Allergy and asthma rates are hypothesized to be on the rise because children's immune systems, no longer challenged by infections, have become oversensitive, attacking the bodies they are supposed to protect. Myopia also correlates with higher IQ scores; U.S. myopia rates in people ages 12 to 54 increased from 25 percent in 1971–72 to 41.6 percent in 1999–2004. But higher IQ correlates with better health and longer lives, less propensity to commit crimes, and higher income (although not greater than average personal wealth).

Trade Creates Jobs and Makes People Richer

Benjamin Franklin once declared, "No country was ever ruined by trade." Franklin believed that the free exchange of products across borders was good for everybody, "even seemingly the most disadvantageous." But in the 21st century, many voters and the politicians they elect believe the opposite. Being open to trade, people fear, allows rapacious corporations to "ship jobs overseas."

A March 2011 European Economic Review study forthrightly asks the question: Does exposure to international trade create or destroy jobs? The answer strongly backs Franklin's observation. "A 10 percent increase in total trade openness reduces aggregate unemployment by about three quarters of one percentage point," the authors conclude. Simply put: Trade creates jobs.

Trade openness is generally measured by adding together the value of a country's exports and imports, then dividing that sum by total gross domestic product (GDP). In other words, the higher a country's volume of international trade, the higher its degree of trade openness. So the U.S. GDP in 2010 was roughly $15 trillion in 2010; exports and imports combined totaled just over $4 trillion, yielding a trade openness index figure of around 27 percent.

Why does free trade create more jobs? The European Economic Review study suggests that freer trade boosts overall productivity, enabling companies to hire more workers. Trade enhances competition, which weeds out inefficient firms and allows more productive ones to expand. As the average efficiency of firms in a country increases, they can earn more revenues by boosting production. And that leads to hiring additional workers.

Trade openness also improves the lives and livelihoods of women. A 2012 study by two German economists, Niklas Potrafke of the University of Munich and Heinrich Ursprung of Konstanz University, examined the relationship: "Observing the progress of globalization for almost one hundred developing countries at ten year intervals starting in 1970, we find that economic and social globalization exert a decidedly positive influence on the social institutions that reduce female subjugation and promote gender equality."

A 2005 study in World Development by the London School of Economics economists Eric Neumayer and Indra De Soysa found that "countries that are more open towards trade and/or have a higher stock of foreign direct investment also have a lower incidence of child labor." Openness to trade also correlates with higher school attendance rates. This finding suggests that legislation such as the recent bill proposed by Sen. Tom Harkin (D-Iowa) restricting imports made using child labor would actually backfire, forcing kids to work at less secure and less well-paying jobs in the informal sector.

Trade openness is additionally coupled with higher per capita incomes. In 2009, economists Vlad Manole of the Conference Board in New York and Mariana Spatareanu of Rutgers devised a trade restriction index to probe the degree of trade protection in the economies of 131 countries using data between 1990 and 2004. They found that "a 1 percent decrease in trade restrictiveness leads to an approximately 0.3 percent increase in income per capita."

So why do people, especially politicians, believe that freer trade increases unemployment, hurts women and children, and reduces incomes? The 19th century French economist Frederic Bastiat explained this sort of disheartening policy myopia in his brilliant essay, "What is Seen and What is Not Seen." People tend to focus on the seen consequences of a policy, such as competition from trade eliminating some jobs at relatively inefficient companies. And they miss the unseen benefits, such as the new jobs that result from increased average productivity.

The protectionist politics that follow from this misdiagnosis mean that a few seen workers get to keep their jobs while a much larger number of unseen jobs never get created in the first place. Meanwhile, the same laws make other Americans worse off by forcing them to spend more, because they are denied access to less expensive imports.

Local Biodiversity Is Increasing

Ascension Island is about as isolated as a piece of land can get, sitting in the Atlantic Ocean about midway between Africa and South America. When the British claimed authority over the uninhabited, barren hunk of stone in the early 19th century, it was frequently likened to a "cinder" or a "ruinous heap of rocks." The new owners named Ascension's central peak White Mountain, after the color of the bare rocks of which it was composed.

In 1846, botanist John Hooker from the Royal Botanical Gardens at Kew visited and decided to try transplanting a wide variety of plants onto the island. A century and a half later, the result has been an "accidental rainforest." White Mountain, now renamed Green Mountain, is covered with an extensive cloud forest consisting of guava, banana, wild ginger, bamboo, the Chinese glory bower and Madagascan periwinkle, Norfolk Island pine, and eucalyptus from Australia. Because of the man-made micro-climate, what used to be a desert island now features several permanent streams.

Ascension Island undercuts the conventional ecological wisdom that tropical rainforests are supposed to take millions of years to form. And what happened on Ascension has been happening all around the world, as people have moved thousands of species from their native habitats to new locales, increasing species richness. Wherever human beings have gone in the past two centuries, we have increased local and regional biodiversity.

Yet "the popular view [is] that diversity is decreasing at local scales," the Brown biologist Dov Sax and the University of California–Santa Barbara biologist Steven Gaines report in a 2003 article for Trends in Ecology and Evolution. Sax and his University of New Mexico colleague James Brown point out in a 2007 roundtable in Conservation that "North America presently has more terrestrial bird and mammal species than when the first Europeans arrived five centuries ago."

While some introduced species do outcompete natives and contribute to their extinction, that phenomenon is relatively rare. On the whole, the actual number of species in any given area has tended to increase. For example, New Zealand's 2,000 native plant species have been joined by 2,000 from elsewhere, doubling the plant biodiversity of its islands. Meanwhile, only three species of native plants have gone extinct. In California, an additional 1,000 new species of vascular plants have joined the 6,000 native species in the Golden State, while just 40 species have gone extinct. Similar increases in plant diversity can be seen around the globe.

The species that have become extinct and are most in danger of extinction are those that dwell in isolated habitats such as oceanic islands or freshwater streams. In a 2008 article for the Proceedings of the National Academy of Sciences, Sax and Gaines note that thousands of oceanic bird species went extinct as Polynesians spread across the Pacific bringing not only themselves but hungry rats. Nevertheless, they point out, the overall species richness of the plant life on Pacific islands has increased considerably, and bird species richness has remained about the same, since the number of extinctions has been balanced by a number of new species moving in.

Mammalian and freshwater species richness has dramatically increased on Pacific islands as well—it was much harder for animals like rats, pigs, deer, lizards, frogs, catfish, and trout to colonize islands on their own. In addition, while some freshwater species in continental streams and lakes have gone extinct, most now harbor more species than they did before. Hawaii is, for example, home to more than 2,500 new species of invertebrates.

In many cases, the newcomers may actually benefit the natives. In a 2010 review article in the Annual Review of Ecology, Evolution, and Systematics, the Rutgers ecologist Joan Ehrenfeld reported that rapidly accumulating evidence from many introduced species of plants and animals shows that they improve ecosystem functioning by increasing local biomass and speeding up the recycling of nutrients and energy. For example, zebra mussels are very effective filter feeders that have helped clear up the polluted waters of the Great Lakes enough to permit native lake grasses and other plants to flourish.

"Imagine that an alien scientist from outer space were to visit both New Zealand and Great Britain," write Sax and Gaines. "Would this individual be able to distinguish which species are native and exotic, and would it be able to demonstrate that invaders have caused more damage or disruption to ecological processes than natives?" The answer to both questions is no.

Markets Make People Nicer

In The Communist Manifesto, Karl Marx thundered that the bourgeoisie and the markets that allow them to prosper "left remaining no other nexus between man and man than naked self-interest, than callous 'cash payment.'?" In other words, markets destroy fellow-feeling, turning human beings into cold, cruel calculators. But recent research on how 15 small-scale societies play certain canonical economic games suggests that simply isn't so.

The societies investigated by the economists and anthropologists organized as the MacArthur Foundation's Norms and Preferences Network ranged from hunter-gatherers to slash-and-burn horticulturalists on five continents. To probe these societies' attitudes toward sharing and fairness, the researchers had their members play several games. One of these is called the Ultimatum Game. In it, researchers provisionally allot a divisible pie ($10, say) to one player. This player, the "proposer," offers a portion of the pie to the second subject, the "responder." The responder, who knows both the offer and the total amount of the pie, chooses to either accept or reject the offer. If the responder accepts, he or she gets the amount offered and the proposer gets the remainder. If the responder rejects the offer, neither player receives anything.

Rationally speaking, one might expect that the proposer would offer as little as possible ($1, say) and that the responder would never reject an offer because, after all, one dollar is better than nothing. Yet in hundreds of experiments in nearly two dozen countries, subjects rarely act in that purely self-interested way. In modern societies, the most frequent amount offered by proposers is 50 percent, and responders commonly reject offers under a third. After examining a number of different explanations, most researchers have concluded that those choices are based on the players' sense of what is fair. Since these experiments are usually conducted using western undergraduates, the Preference Network researchers wondered if the results would hold true across societies.

The experimenters offered participants the equivalent of a day or two's wages in their societies. The researchers found that the average offers from proposers ranged from a low of 26 percent to a high of 58 percent and that the most frequent offers ranged from 15 percent to 50 percent. Some groups, such as the Machiguenga and Quichua in South America and the Hadza in Africa, offered around 25 percent of the pie. The most frequent offer from the Machiguenga proposers was 15 percent. Only one Machiguenga responder rejected such a low offer.

Societies like the Machiguenga and Hadza, which deal with few outsiders and are not economically dependent on people other than close kin, turn out to be the stingiest players. The Orma in Africa and the Achuar in South America, who are more integrated into markets, tend to play more like the western undergraduates. "The higher the degree of market integration and the higher the payoffs of cooperation, the greater the level of prosociality found in experimental games," the researchers found.

Herbert Gintis, co-director of the Preference Network team, speculates that markets bring strangers into contact on a regular basis, encouraging people to develop more concern for others beyond their family and immediate neighbors. Instead of parochialism, being integrated into markets encourages a spirit of ecumenism. "Extensive market interactions may accustom individuals to the idea that interactions with strangers may be mutually beneficial," the researchers theorize. "By contrast, those who do not customarily deal with strangers in mutually advantageous ways may be more likely to treat anonymous interactions as hostile, threatening, or occasions for opportunistic pursuit of self-interest."

Markets teach participants the habits of cooperation, trust, and fairness. Based on his research, Gintis argues that history traces humanity's ascent from tribal selfishness to more cosmopolitan liberality. "Market societies give rise to more egalitarianism and movements toward democracy, civil liberties, and civil rights," Gintis argues. "Market societies and democratic societies are practically co-extensive." And they are more generous too.