Before an ipo the company must let the s-1-registration do the talking; promotional statements outside it can be treated as illegal gun-jumping and delay the deal. After the debut, the underwriters' research analysts are barred from publishing for a set number of days.
That second window creates a predictable event. When it lapses, a cluster of buy ratings from the very banks that sold the deal appears on the same morning, which is why analyst-coverage initiations are rarely a surprise in direction, only in price targets.
Example: a company lists on 3 March. Underwriter research is blocked until the quiet period lapses, and on the morning it does, seven of the eight syndicate banks initiate at buy with targets 20% to 45% above the current price.
Related: ipo, analyst-coverage, s-1-registration, underwriter, roadshow