DES MOINES — Drake University in Des Moines is guaranteeing that next fall’s incoming students will pay the same tuition each year until they graduate. Drake officials think their Drake Tuition Guarantee program is the first of its kind in the state and also among the private university’s official peer institutions. Drake President Early Martin says the plan is designed to help increase enrollment and retention. Martin says Drake students have seen an annual average increase of 4.5 percent over the past five years.