From the passage provided, extract the year Adani group was founded.

Adani Group is an Indian multinational conglomerate, headquartered in Ahmedabad. It was founded by Gautam Adani in 1988 as a commodity trading business, with the flagship company Adani Enterprises. The Group's diverse businesses include port management, electric power generation and transmission, renewable energy, mining, airport operations, natural gas, food processing and infrastructure.[4]

In April 2021, Adani Group crossed US$100 billion in market capitalization, and in April 2022 it crossed the $200 billion mark, in both cases becoming the third Indian conglomerate to do so, after Tata Group and Reliance Industries.[5][6] In November 2022, it reached $280 billion (INR 24 trillion) surpassing Tata Group.[7] Adani subsequently lost more than $104 billion of market capitalization after fraud and market manipulation allegations by short-seller firm Hindenburg Research.[8] The Adani Group has also attracted other controversies due to various reports of irregular practices.[9][10][11] More than 60 percent of the Adani Group's revenue is derived from coal-related businesses.[12] The company's corporate debt totaled $30 billion in 2022.[13]

Adani group was founded in 1988