Saudi Arabia’s sovereign wealth fund, a key engine of the kingdom’s plan to diversify the economy, on Wednesday laid out new targets for growth, saying it aims to nearly double the value of assets it manages to around $400 billion by 2020. That sum includes the expected proceeds from the planned initial public offering of up to 5% of state-owned oil giant Saudi Aramco. The listing, slated for next year, could raise as much as $100 billion, Saudi officials have said.