We study an implicit contract model to shed light on the relationshipbetween the closedness of public service recruitment system and the corruptionrampant between private firms and public servants. By introducing access costwhich depends on the personal affinity between a predecessor and a successorin the hierarchy of public bureaucracy, we can explain why a bureaucracyfilled with closed recruitment system is more corrupted than one with openrecruitment system, which is a stylized fact that we found from OECD andIMD data. We show that the more open the recruitment system, the harderto sustain the implicit corruption contract between a public official and a privatecompany.