Trusov, Bucklin, Pauwels 2009 (JoM) — WOM elasticity on signups ≈ 0.53, roughly 20× marketing-events elasticity, 30× media-appearance elasticity

Claim: Trusov, Bucklin, and Pauwels (2009), "Effects of Word-of-Mouth versus Traditional Marketing: Findings from an Internet Social Networking Site," found:

• WOM elasticity on signups ≈ 0.53
• ~20× elasticity of marketing events
• ~30× elasticity of media appearances
• WOM carryover was substantially longer than paid-marketing carryover

Source: Trusov, M., Bucklin, R. E., & Pauwels, K. (2009). Journal of Marketing 73(5), 90–102.

Confidence: Verified (single-firm, online social network). Magnitude is not portable to construction at face value; directional finding (WOM has higher amplitude + longer carryover than paid) has been replicated across multiple settings.

For Candid: The point is not "WOM is 20× better than events in trades" — that figure is from an online-signup context. The point is that WOM and paid marketing operate on different decay curves: paid is high-decay, requires continuous spend; WOM is low-decay, compounds. In a buying cycle where decisions are made every 3-7 years (trades), low-decay channels dominate over time.

Related: [[apb-sorci-2024-48-7pct-referrals-half-of-sales]] gives the in-domain referral-volume anchor (48.7% of residential builders source >50% of sales from referrals).