Question: What was the population of Kowloon City, an area in Kowloon, Hong Kong, by 1990?

Context paragraphs:
New Kowloon: New Kowloon is an area in Kowloon, Hong Kong, bounded in the south by Boundary Street, and in the north by the ranges of the Lion Rock, Beacon Hill, Tate's Cairn and Kowloon Peak.  It covers the present-day Kwun Tong District and Wong Tai Sin District, and part of the Sham Shui Po District and Kowloon City District.

Kowloon West New Dynamic: Kowloon West New Dynamic is a centre-right political party in Hong Kong.  It was founded by a group of local politicians in the Kowloon West area on 16 March 2008.  The main focus of party is to improve quality of life in the districts within the area which including Sham Shui Po District, Kowloon City District, and Yau Tsim Mong District.  Priscilla Leung is the current chairman.The party currently holds 7 seats in the District Council of Hong Kong and 1 seat in Legislative Council of Hong Kong.

Kowloon Tsai Park: Kowloon Tsai Park is a park located in the Kowloon Tsai area of New Kowloon in Hong Kong.  It lies within the Kowloon City District and opened in June 1964.

Kowloon City District Council: Kowloon City District Council () is the district council for the Kowloon City District in Hong Kong.  It is one of 18 district council.  Kowloon City District currently consists of 24 members, of which the district is divided into 24 constituencies, electing a total of 24 members.  The latest election was held in 2015.

Grand Waterfront: Grand Waterfront () is a private housing estate and a shopping mall in Ma Tau Kok, Kowloon, Hong Kong, near Kowloon City Ferry Pier.  Formerly the Hong Kong and China Gas gaswork site, the estate consists of five 62-storey high-rise buildings and a shopping arcade.  It was jointly developed by Henderson Land Development and Hong Kong and China Towngas and completed in 2007.

Kowloon City Plaza: Kowloon City Plaza (KCP;) is a shopping mall located at Kowloon City, Kowloon, Hong Kong.  It was established in December 1993, and it underwent a major renovation by a company named Pamfleet with 100 million Hong Kong dollars (HKD) from October 2005 to December 2006.  The mall re-opened on 26 January, 2007.

Kowloon City: Kowloon City () is an area in Kowloon, Hong Kong.  It is named after the Kowloon Walled City, and is administratively part of Kowloon City District.

Kowloon Tsai: Kowloon Tsai (Chinese: 九龍仔) is a place between Kowloon City and Kowloon Tong in Hong Kong.  It was formerly a village in valley and now the place became low density residential area in New Kowloon.  Due to the ambiguity of the area's west boundary (Junction Road serves as Kowloon Tsai's east boundary) and the opening of the nearby Kowloon Tong Station in 1979, it is now frequently regarded as a part of the Kowloon Tong area.

Kowloon Walled City: Kowloon Walled City was a largely-ungoverned densely-populated settlement in Kowloon City in Hong Kong.  Originally a Chinese military fort, the Walled City became an enclave after the New Territories were leased to Britain by China in 1898.  Its population increased dramatically following the Japanese occupation of Hong Kong during World War II.  By 1990, the Walled City contained 50,000 residents within its 2.6 ha borders.  From the 1950s to the 1970s, it was controlled by local triads and had high rates of prostitution, gambling and drug abuse.

Kowloon Tong: Kowloon Tong () is an area of Hong Kong located in Kowloon West.  The majority of the area is in the Kowloon City District.  It is located south of Beacon Hill, north of Boundary Street, east of Shek Kip Mei, and west of Kowloon Tsai and Lok Fu.  It is an expensive, low density and quiet residential district, with housing comprising mainly bungalows and villas.  It is popular among the upper class in the city because it has many prestigious schools.  In addition, this area is noted for its love hotels and nursing homes.  Within Kowloon West, it is administratively divided between Kowloon City District and Sham Shui Po District.

Supporting paragraphs: Kowloon City Kowloon Walled City
Answer: 50,000 residents