pre_text: a e s 2 0 0 0 f i n a n c i a l r e v i e w in may 2000 , a subsidiary of the company acquired an additional 5% ( 5 % ) of the preferred , non-voting shares of eletropaulo for approximately $ 90 million . in january 2000 , 59% ( 59 % ) of the preferred non-voting shares were acquired for approximately $ 1 billion at auction from bndes , the national development bank of brazil . the price established at auction was approximately $ 72.18 per 1000 shares , to be paid in four annual installments com- mencing with a payment of 18.5% ( 18.5 % ) of the total price upon closing of the transaction and installments of 25.9% ( 25.9 % ) , 27.1% ( 27.1 % ) and 28.5% ( 28.5 % ) of the total price to be paid annually thereafter . at december 31 , 2000 , the company had a total economic interest of 49.6% ( 49.6 % ) in eletropaulo . the company accounts for this investment using the equity method based on the related consortium agreement that allows the exercise of significant influence . in august 2000 , a subsidiary of the company acquired a 49% ( 49 % ) interest in songas limited for approxi- mately $ 40 million . songas limited owns the songo songo gas-to-electricity project in tanzania . under the terms of a project management agreement , the company has assumed overall project management responsibility . the project consists of the refurbishment and operation of five natural gas wells in coastal tanzania , the construction and operation of a 65 mmscf/day gas processing plant and related facilities , the construction of a 230 km marine and land pipeline from the gas plant to dar es salaam and the conversion and upgrading of an existing 112 mw power station in dar es salaam to burn natural gas , with an optional additional unit to be constructed at the plant . since the project is currently under construction , no rev- enues or expenses have been incurred , and therefore no results are shown in the following table . in december 2000 , a subsidiary of the company with edf international s.a . ( 201cedf 201d ) completed the acquisition of an additional 3.5% ( 3.5 % ) interest in light from two sub- sidiaries of reliant energy for approximately $ 136 mil- lion . pursuant to the acquisition , the company acquired 30% ( 30 % ) of the shares while edf acquired the remainder . with the completion of this transaction , the company owns approximately 21.14% ( 21.14 % ) of light . in december 2000 , a subsidiary of the company entered into an agreement with edf to jointly acquire an additional 9.2% ( 9.2 % ) interest in light , which is held by a sub- sidiary of companhia siderurgica nacional ( 201ccsn 201d ) . pursuant to this transaction , the company acquired an additional 2.75% ( 2.75 % ) interest in light for $ 114.6 million . this transaction closed in january 2001 . following the purchase of the light shares previously owned by csn , aes and edf will together be the con- trolling shareholders of light and eletropaulo . aes and edf have agreed that aes will eventually take operational control of eletropaulo and the telecom businesses of light and eletropaulo , while edf will eventually take opera- tional control of light and eletropaulo 2019s electric workshop business . aes and edf intend to continue to pursue a fur- ther rationalization of their ownership stakes in light and eletropaulo , the result of which aes would become the sole controlling shareholder of eletropaulo and edf would become the sole controlling shareholder of light . upon consummation of the transaction , aes will begin consolidating eletropaulo 2019s operating results . the struc- ture and process by which this rationalization may be effected , and the resulting timing , have yet to be deter- mined and will likely be subject to approval by various brazilian regulatory authorities and other third parties . as a result , there can be no assurance that this rationalization will take place . in may 1999 , a subsidiary of the company acquired subscription rights from the brazilian state-controlled eletrobras which allowed it to purchase preferred , non- voting shares in eletropaulo and common shares in light . the aggregate purchase price of the subscription rights and the underlying shares in light and eletropaulo was approximately $ 53 million and $ 77 million , respectively , and represented 3.7% ( 3.7 % ) and 4.4% ( 4.4 % ) economic ownership interest in their capital stock , respectively . the following table presents summarized financial information ( in millions ) for the company 2019s investments in 50% ( 50 % ) or less owned investments accounted for using the equity method: .
post_text: .
table: As of and for the Years ended December 31, 2000 1999 1998
table: Revenues $6,241 $5,960 $8,091
table: Operating Income 1,989 1,839 2,079
table: Net Income 859 62 1,146
table: Current Assets 2,423 2,259 2,712
table: Noncurrent Assets 13,080 15,359 19,025
table: Current Liabilities 3,370 3,637 4,809
table: Noncurrent Liabilities 5,927 7,536 7,356
table: Stockholder's Equity 6,206 6,445 9,572
question: Analyse this data from a financial earnings document. what was the change in revenue for the company 2019s investments in 50% ( 50 % ) or less owned investments accounted for using the equity method between 1998 and 1999?