Trading of shares in British chip designer Arm begins tomorrow. City eyes will be closely watching stock price moves for the most hotly anticipated tech IPO of the year following the firm’s decision to close its order book early after being oversubscribed by a factor of ten. Arm’s target price range has shifted around somewhat in recent weeks, in signs it is proving difficult to price a big tech company amid a slump in listings. Owner SoftBank had been eyeing a valuation of $60-70 billion for it earlier this year, before setting Arm’s IPO price at $47-51 a share last...