oil taxes to the federal government's revenue hovered at around 12% to 16% until 1980, when it showed a marked increase to 23%, followed by another leap to 32% in 1981. From then until 1988 the proportion fluctuated between 29% and 36%. Petronas was not just another big oil company: it controlled a crucial sector of the economy and remained, for better or worse, an indispensable instrument of the state. Expanding globally: the 1990s and beyond During the mid- to late 1990s, international exploration, development, and production remained key components in Petronas's strategy along with diversification. A key discovery was made in the Ruby field in Vietnam in 1994. That year, the firm also saw its first overseas production from the Dai Hung field in Vietnam and established its first retail station outside of Malaysia in Cambodia. In 1995, a subsidiary was created to import, store, and distribute liquefied petroleum gas (LPG). In addition, the company's polyethylene plant in Kerteh began operations. Petronas marked a significant milestone during this time period—two of its subsidiaries, Petronas Dagangan Bhd and Petronas Gas Bhd, went public on the Kuala Lumpur Stock Exchange. Between 1993 and 1996, it purchased the former sub-Saharaian branch of Mobil Oil, rebranded as Engen Petroleum. In 1996, Petronas entered the aromatics market by way of a joint venture that created Aromatics Malaysia Sdn Bhd. It also formed a contract with China National Offshore Oil Corporation and Chevron Overseas Petroleum Ltd. to begin the exploration of block 02/31 of the Liaodong Bay area in China. While the Asian economy as a whole suffered from an economic crisis during 1997 and 1998, Malaysia was quick to bounce back due to successful government reforms. From its new headquarters in the Petronas Twin Towers, the state-owned concern continued its development in the oil and gas industry. During 1997, Petronas heightened its diversification efforts. The firm set plans in motion to build three petrochemical plants in Kuantan as well as an acetic facility in Kerteh. Its first LPG joint venture in China was launched that year, and the company acquired a 29.3% interest in Malaysia International Shipping Corporation Berhad (MISC). In 1998, Petronas's tanker-related subsidiary merged with MISC, increasing Petronas's stake in MISC to 62%. That year, Petronas introduced the Petronas E01, the country's first commercial prototype engine. The company also signed a total of five new production sharing contracts (PSCs) in 1998 and