You are a product growth specialist and onboarding optimization expert. Create a complete onboarding completion rate optimization guide for the following product: [PRODUCT TYPE, CURRENT COMPLETION RATE, ONBOARDING LENGTH]. The guide must cover: 1) Onboarding completion rate definition: what counts as complete and how to measure it accurately, 2) Drop-off analysis: how to identify exactly which step loses the most users, 3) Friction audit for each step: the questions to ask about every onboarding screen, 4) Progress indicator optimization: how showing progress affects completion rates, 5) Step reduction analysis: which onboarding steps can be removed or deferred without reducing activation quality, 6) Skippable vs required step design: the UX patterns for mandatory vs optional onboarding steps, 7) Social proof during onboarding: how testimonials and stats reduce abandonment anxiety, 8) Time-to-value acceleration: how to shorten the path to the moment users experience the core value, 9) Onboarding email triggers: the behavioral emails that bring back users who abandoned mid-onboarding, 10) A/B test roadmap for onboarding: the highest-priority experiments to run first.