2016 was rough. So rough, in fact, that many media outlets (and tweets and Facebook posts) have crowned it the worst year ever. "2016: Worst. Year. Ever?" asks the New York Times. "Is this the worst year ever, or what?" decried a columnist at Slate. The Wall Street Journal even put together a guide on how to "bid good riddance to the worst year ever."

I get it. But Americans almost always think that the year coming to a close is the worst. At the close of 2015, for example, Americans were asked "Do you think the world is getting better or worse, or neither getting better nor worse?" Only 6 percent of those surveyed thought the world was getting better. The same low numbers were seen in 2000, 2005 and 2010.

Why do Americans have such a negative view? Many misunderstand how the world is changing or ignore positive change.

Over the past decade, for example, extreme poverty across the world has declined tremendously. In 1981, 44 percent of the world lived in extreme poverty. By 2015, extreme poverty dropped to 10 percent. Yet, when Oxfam asked Americans how global extreme poverty is changing, the majority thought that extreme poverty was increasing. Only 8 percent were aware that it's falling.

Other surveys find a similar lack of knowledge about positive developments. Crime rates have fallen for years in the United States, but the majority believe crime is on the rise.

This lack of knowledge about how our world is changing is not new. Surveys from long before 2016 — long before the world turned "post-factual" — show the same levels of ignorance.

There are several reasons for this. To start, the structure of the media means negative subjects are almost always being highlighted. Harm is done in an instant, and disasters are happening at once: an earthquake, a plane crash or a terrorist attack. In contrast to this, the best news for life on Earth — improving global health, falling poverty, environmental progress — are shaped by quiet trends over the course of decades or centuries. The focus on single events and neglect of slow developments selects negative news instead of often positive developments.

In a classic essay from 1965, Johan Galtung analyzed the structure of news. He found that the frequency with which outlets publish — daily, and now instantly — limits their ability to cover long-term positive trends. Imagine if newspapers did not come out every day but instead once every half-century. They likely wouldn't report on half a century of gossip about celebrities and politicians. Instead, they'd focus on major global changes since the last edition.

In a 50-year newspaper, the fact that global child mortality has fallen from 17 percent to 4 percent would make the front page.

The negative bias of event news is a problem on the supply side, but there are equally important problems on the demand side. To be on the lookout for signs of danger is hard-wired in our human psychology. Evolution has shaped us to pay attention selectively and with a negativity bias — because it is much more important for our survival to pay attention to threats than to positive changes. A missed opportunity is unfortunate, an overlooked danger can bring sudden death.

What equipped us well for life in small groups in our long past set us up with a mind that can lapse into a constant state of panic when exposed to the stream of 24-hours news. Even in a world of declining violence, on social media one can always find stories on violence, terror and possible threats.

We can see how the media echo what our human mind pays attention to: This week's announcement of a successful development of a vaccine against Ebola was a footnote in much of the press and will not receive even a fraction of the attention the Ebola scare received when it dominated the news cycles for months.

Another important reason that we are not aware of the slow developments that reshape our world is that we do not learn about them in our educational system. It should not be possible to make it through school without being taught how global living conditions have changed, but since this subject lies between mathematics (statistics) and history, it seems to fall through the cracks.

The consequence of this is that we have no knowledge about the poverty, poor health and the high levels of violence that characterized our past. Only this ignorance makes it possible to tell stories of decline, because it means that we are unaware of how inconceivably exceptional our current living conditions are from the perspective of our ancestors.

The story that we tell about ourselves is the most important story of all. Journalists and intellectuals who almost exclusively focus on what goes wrong risk our losing our faith in one another, and that faith is the essential foundation without which our ideal of a free and democratic society is impossible. A constant supply of news that makes us afraid with little to instill trust in one another and in our institutions has always been the best press demagogues can hope for.

Freedom is impossible without faith in free people, and if we are not aware of our history and produce and demand only information on what goes wrong, we lose faith.

We can do much better instead if we learn about the slow transformations that often change our world for the better and a journalism that sees it as part of its role "to reveal the decency, competence and courage of people determined to fix their society."

Max Roser is an economist and media critic at the University of Oxford. He wrote this article for the Washington Post.