On Jan. 17, the price of the cryptocurrency Bitcoin dipped below $10,000, a 50 percent decline from its record peak in December 2017. Bitcoin, which was first released in 2009, has a history of price fluctuations. Excitement over virtual currencies grew in 2017, when Wall Street and small investors in Japan and South Korea expressed interest in them, leading to a surge of ordinary investors putting their money into Bitcoin. Economists speculated that the bust was fueled by fear of regulatory crackdowns on cryptocurrency trading.
HIGH SCHOOL SHOOTING PROMPTS GUN CONTROL DEBATE IN FLORIDA
Seventeen students and adults were killed at Marjory Stoneman Douglas High School in Parkland, Fla., on Feb. 14 when 19-year-old Nikolas Cruz, who was previously expelled from the school, opened fire inside and outside the building with a semiautomatic AR-15 assault rifle. The massacre prompted a national debate over gun control. While the National Rifle Association proposed arming teachers to better protect against school shootings, anti-gun groups and Parkland students pushed for reform. Just over three weeks after the shooting, Florida Gov. Rick Scott signed into law a number of firearm restrictions, breaking with N.R.A. opposition.
XI JINPING COULD RULE INDEFINITELY
On March 11, the nearly 3,000 delegates of China's Communist-controlled National People's Congress almost unanimously approved an amendment to the Constitution abolishing presidential term limits, enabling President Xi Jinping to rule indefinitely. The two-term limit was part of a political order put in place by Deng Xiaoping, a reform-era leader. In addition to the presidency, Mr. Xi holds the positions of Communist Party general secretary and military chief, neither of which have term limits.
RAÚL CASTRO STEPS DOWN AS CUBA'S PRESIDENT
Raúl Castro brought an end to nearly six decades of Castro family rule when he stepped down as president of Cuba on April 19. The National Assembly named the Communist Party loyalist and First Vice President Miguel Díaz-Canel, 58, as Mr. Castro's successor. The selection of Mr. Díaz-Canel marked an important shift of power in Cuba to a younger generation of leaders, many of whom were born after the country's revolution. Despite his departure from the presidency, Mr. Castro, 87, announced that he would still remain head of the Communist Party until 2021.
TRUMP WALKS AWAY FROM NUCLEAR DEAL
American President Donald Trump ignited outrage from allies of the United States around the globe when he announced on May 8 that he was withdrawing from the Iran nuclear deal. The landmark deal was reached in July 2015 under the Obama administration and lifted sanctions on Iran's oil and financial sectors in exchange for the country accepting restrictions to its nuclear program. Mr. Trump's withdrawal fulfilled an early campaign promise to exit the deal, but his decision was met with criticism from leaders of other countries in the agreement. France, Germany and Britain announced they intended to preserve the deal.
WOMEN IN SAUDI ARABIA START DRIVING
Saudi women were legally able to drive for the first time in the kingdom's history on June 24, after Saudi Arabia officially lifted a decades-long ban. The country, the last in the world in which women could not drive, has seen years of campaigning by women's rights activists who have sometimes been arrested and detained for their efforts. Though the lifting of the ban was championed by Crown Prince Mohammed bin Salman, the king's 33-year-old son who has ordered other recent changes to improve Saudi life, it came amid continued arrests of women's advocates.
VICTORY FOR LÓPEZ OBRADOR
On July 1, Andrés Manuel López Obrador declared victory in Mexico's presidential election, becoming the country's first leftist leader in more than three decades. The veteran politician, commonly referred to by his initials AMLO, won the presidency by a landslide in which he received 53 percent of the vote. Mr. López Obrador campaigned on a promise to usher in a new era of Mexican politics, as well as to stand up to President Trump. In his victory speech, he vowed to take on high-level corruption, fight organized crime and tackle Mexico's endemic poverty.
PLANS FOR A CENSORED SEARCH ENGINE IN CHINA
News of Google's plan to launch a censored version of its search engine in China was leaked to the public on Aug. 1, prompting outrage from human rights groups and employees of the internet giant. The modified search engine would restrict content and search terms banned by the Chinese government. The project, given the code-name "Dragonfly," began in early 2017 and marked a significant reversal for Google in China: In 2010, the company shut down its Chinese search engine in protest of censorship and online hacking in the country.
A BUFFER ZONE IN SYRIA'S IDLIB PROVINCE
On Sept. 17, Russian President Vladimir Putin and Turkish President Recep Tayyip Erdogan reached an agreement establishing a demilitarized buffer zone in the Idlib region of Syria. The two leaders created the zone in an effort to prevent military conflict between the Syrian government and rebel forces in Idlib, as fears mounted that Syrian President Bashar al-Assad was preparing to launch an offensive on the last rebel stronghold. By allowing opposition supporters to stay in the demilitarized zone, which is home to about three million civilians, Mr. Erdogan explained he hoped to avoid a migrant crisis in Turkey.
POLICE ARREST SUSPECTS IN TERRORIST RING IN GERMANY
German police arrested six men suspected of forming a far-right terrorist group in the city of Chemnitz on Oct. 1. A seventh man, who was arrested in a separate case in September, was believed to be the group's leader. Federal prosecutors suspect that the men, all German nationals aged between 20 and 30, operated under the name "Revolution Chemnitz" and had been planning to carry out armed attacks on foreigners and political enemies. Discovery of the terrorist ring came weeks after the fatal stabbing of a German man and the subsequent arrests of two immigrants in Chemnitz. Protests and violence between extremist groups and the police followed, reigniting tensions over Germany's immigration debate.
NASA'S INSIGHT SPACECRAFT LANDS ON MARS
NASA's InSight lander touched down on Mars on Nov. 26 after a six-month journey of more than 300 million miles. The lander, built by scientists in the United States and Europe, will spend about two Earth years searching the planet for clues about its formation and history, using radio antennas, a seismometer and a heat sensor to collect data. Scientists hope the $1 billion project will help them better understand how Mars and other rocky planets were formed.
POLITICAL LEADERS NEGOTIATE CLIMATE PACT
World leaders and climate-change experts gathered in Katowice, Poland, on Dec. 2 to put into final form the "rule book" of the 2015 Paris climate agreement. The annual Conference of the Parties to the United Nations Framework Convention on Climate Change brought together representatives from nearly 200 countries. Days before, the U.N. Environment Program released a report warning that many nations' efforts to lower carbon emissions are falling short of the goal, set in 2015, of limiting a temperature increase to 2 degrees Celsius. Global carbon emissions hit a record high in 2017.