Sponsoredsearchadvertisingisasignificantrevenuesourceforsearchengines.Toamelioraterevenues,searchenginesoftensetfixedorvariablereservepricetoininfluenceadvertisers'bidding.Thispaperstudiestheoptimalreservepriceforageneralizedsecond-priceauction(GSP)underbothstaticanddynamicsettings.Weshowthatifadvertisers'per-clickvaluehasanincreasinggeneralizedfailurerate,thesearchengine'srevenuerateisquasi-concaveandhencethereexistsanoptimalreservepriceunderbothsettings.DifferentfromastaticGSPauctionwheretheoptimalreservepriceisprovedtobeconstant,inadynamicsettingtheoptimalreservepriceisdependentonnotonlyadvertisers'per-clickvalues,butalsothenumberofadlinkssold.Asearchengineshouldgraduallyraisereservepriceasmorequalifiedadvertisersarrive,andmaintainthesamethresholdafterallfirst-pagepositionsareoccupied.
