Question: When did the maker of the Acura EL, the company that owns Scion, and Nissan, open US assembly plants?

Knowledge 1: Acura EL
The Acura EL is a subcompact executive car that was built at Honda's Alliston, Ontario, plant, and also the first Acura built in Canada. The EL is a badge-engineered Honda Civic with a higher level of features. [SEP] Knowledge 2: 1973 oil crisis
Some buyers lamented the small size of the first Japanese compacts, and both Toyota and Nissan (then known as Datsun) introduced larger cars such as the Toyota Corona Mark II, the Toyota Cressida, the Mazda 616 and Datsun 810, which added passenger space and amenities such as air conditioning, power steering, AM-FM radios, and even power windows and central locking without increasing the price of the vehicle. A decade after the 1973 oil crisis, Honda, Toyota and Nissan, affected by the 1981 voluntary export restraints, opened US assembly plants and established their luxury divisions (Acura, Lexus and Infiniti, respectively) to distinguish themselves from their mass-market brands. [SEP] Knowledge 3: Scion (automobile)
Scion is a discontinued marque of Toyota that started in 2003. It was designed as an extension of its efforts to appeal towards younger customers. The Scion brand primarily featured sports compact vehicles (primarily badge engineered from Toyota's international models), a simplified "pure price" model, and eschewed trim levels in favor of offering a single trim for each vehicle with a range of factory and aftermarket options for buyers to choose from to personalize their vehicle. The "Scion" name, meaning the descendant of a family or heir, refers both to the brand's cars and their owners. The brand first soft launched in the United States at selected Toyota dealers in the state of California in June 2003, before expanding nationwide by February 2004. In 2010, Scion expanded into Canada. In an effort to target the generation Y demographic, Scion primarily relied on guerrilla and viral marketing techniques.
Knowledge 1: Scion (automobile)
Scion is a discontinued marque of Toyota that started in 2003. It was designed as an extension of its efforts to appeal towards younger customers. The Scion brand primarily featured sports compact vehicles (primarily badge engineered from Toyota's international models), a simplified "pure price" model, and eschewed trim levels in favor of offering a single trim for each vehicle with a range of factory and aftermarket options for buyers to choose from to personalize their vehicle. The "Scion" name, meaning the descendant of a family or heir, refers both to the brand's cars and their owners. The brand first soft launched in the United States at selected Toyota dealers in the state of California in June 2003, before expanding nationwide by February 2004. In 2010, Scion expanded into Canada. In an effort to target the generation Y demographic, Scion primarily relied on guerrilla and viral marketing techniques. [SEP] Knowledge 2: 1973 oil crisis
Some buyers lamented the small size of the first Japanese compacts, and both Toyota and Nissan (then known as Datsun) introduced larger cars such as the Toyota Corona Mark II, the Toyota Cressida, the Mazda 616 and Datsun 810, which added passenger space and amenities such as air conditioning, power steering, AM-FM radios, and even power windows and central locking without increasing the price of the vehicle. A decade after the 1973 oil crisis, Honda, Toyota and Nissan, affected by the 1981 voluntary export restraints, opened US assembly plants and established their luxury divisions (Acura, Lexus and Infiniti, respectively) to distinguish themselves from their mass-market brands. [SEP] Knowledge 3: Acura EL
The Acura EL is a subcompact executive car that was built at Honda's Alliston, Ontario, plant, and also the first Acura built in Canada. The EL is a badge-engineered Honda Civic with a higher level of features.
Knowledge 1: Acura EL
The Acura EL is a subcompact executive car that was built at Honda's Alliston, Ontario, plant, and also the first Acura built in Canada. The EL is a badge-engineered Honda Civic with a higher level of features. [SEP] Knowledge 2: 1973 oil crisis
Some buyers lamented the small size of the first Japanese compacts, and both Toyota and Nissan (then known as Datsun) introduced larger cars such as the Toyota Corona Mark II, the Toyota Cressida, the Mazda 616 and Datsun 810, which added passenger space and amenities such as air conditioning, power steering, AM-FM radios, and even power windows and central locking without increasing the price of the vehicle. A decade after the 1973 oil crisis, Honda, Toyota and Nissan, affected by the 1981 voluntary export restraints, opened US assembly plants and established their luxury divisions (Acura, Lexus and Infiniti, respectively) to distinguish themselves from their mass-market brands. [SEP] Knowledge 3: Scion xB
The Scion xB is a compact car (subcompact car in its first generation) made by Toyota for the United States market and sold under their youth-oriented Scion brand. It is a box-shaped, 5-door hatchback.

Answer: 1981