Question: In which year did the USSR collapse?
About the article "October Revolution", section "Impact of the dissolution of the USSR on historical research".

Candidate passages:
The USSR rebuilt its rail system and industrialized with five-year plans.
As a result, railroad freight grew about 20 times from 20 to 400 billion tonne-km by 1941.
But then disaster struck again: World War II in 1941 when Nazi Germany invaded the Soviet Union.
In the first year or so of the war, traffic plummeted to about half its prewar value.
But then the USSR started restoring and constructing railroads during wartime so that by the end of the war about half of the lost traffic had been recovered.
After the war was over it took a few more years to restore the railroads and get back to the pre-war level of traffic.
Then the USSR embarked on a series of more five-year plans and rail traffic rapidly increased.
By 1954 their rail freight traffic (about 850 billion tonne-km) surpassed that of the United States and the USSR then hauled more rail freight than any other country in the world.
Rail freight continued to rapidly increase in the USSR so that by 1960 the USSR was hauling about half of all railroad freight in the world (in tonne-km) and they did this on a rail system consisting of only 10% of the world's railway kilometrage.
The status of hauling half the world's rail freight continued for almost 30 years but in 1988 rail freight traffic peaked at 3852 billion tonne-km (nearly 4 trillion).
And then, a few years later in 1991, the Soviet Union fell apart and its largest republic, the Russian Federation, which then hauled about 2/3 of the traffic of the former USSR, became an independent country.
For the USSR in 1989 (shortly before the collapse), the railroads hauled nearly eight times as much ton-km of freight by rail as they did by highway truck.
For the US, it was only 1.5 times as much by rail.
Thus trucks in the USSR played a far lesser role in hauling freight than they did in the US, leaving the railroad as the basic means of freight transportation.
In 1991 a law was passed which declared that railroads were the basic transportation system of the USSR. 
During the collapse of USSR Nagorno-Karabakh War started and all Azerbaijani populations were deported by Armenian forces from Nagorno-Karabakh region. 
The graph compares the freight traffic (in ton-km) of the USSR to the US.
The USSR rebuilt its rail system and industrialized with five-year plans.
As a result, railroad freight grew about 20 times from 20 to 400 billion tonne-km by 1941.
But then disaster struck again: World War II in 1941 when Nazi Germany invaded the Soviet Union.
In the first year or so of the war, traffic plummeted to about half its prewar value.
But then the USSR started restoring and constructing railroads during wartime so that by the end of the war about half of the lost traffic had been recovered.
After the war was over it took a few more years to restore the railroads and get back to the pre-war level of traffic.
Then the USSR embarked on a series of more five-year plans and rail traffic rapidly increased.
By 1954 their rail freight traffic (about 850 billion tonne-km) surpassed that of the United States and the USSR then hauled more rail freight than any other country in the world.
Rail freight continued to rapidly increase in the USSR so that by 1960 the USSR was hauling about half of all railroad freight in the world (in tonne-km) and they did this on a rail system consisting of 10% of the world's railway kilometrage.
The status of hauling half the world's rail freight continued for almost 30 years but in 1988 rail freight traffic peaked at 3852 billion tonne-km (nearly 4 trillion).
This rapid growth may seem impressive, but it was in part a failure because rail traffic at times didn't grow fast enough to satisfy demand, partly due to congestion.
In 1991 the Soviet Union fell apart and its largest republic, the Russian Federation, which then hauled about 2/3 of the traffic of the former USSR, became an independent country.
For the USSR in 1989, shortly before the collapse of Soviet Union, the railroads hauled nearly eight times as much ton-km of freight by rail as they did by highway truck.
In 1991 a law was passed which declared that railroads were the basic transportation system of the USSR. 
This is a List of the heads of government of the Group of 8 nations at each G8 Summit since the Group's inception in 1975.
The Group consists of the eight largest industrialized democracies, Canada, France, Germany, Italy, Japan, Russia, the United Kingdom and the United States.
Also in attendance is the President of the European Commission, who represents the European Union.
The G8 holds an annual summit, which each nation's head of government attends.
Each year the heads of government take turns assuming the presidency, whose job it is to set the agenda for and host the annual summit.
The leader who has been in office the longest of the eight leaders is considered the Senior G8 leader.
While the current G8 consists of eight nations, it did not always.
The group was formed as the Group of Six, G6, including all of today's members minus Canada and Russia, which at the time was still the Union of Soviet Socialist Republics, the USSR.
Under the leadership of Prime Minister Pierre Trudeau, Canada joined in the second year of the group's existence, 1976, forming the Group of Seven, G7.
Russia, as the successor nation to the USSR, joined the group in 1997, following the collapse of its Communist predecessor, under the leadership of President Boris Yeltsin. 
The economist Ravi Batra predicted the collapse of the USSR in his 1978 book "The Downfall of Capitalism and Communism".