The Lean Startup - Eric Ries [86]
The Viral Engine of Growth
Online social networks and Tupperware are examples of products for which customers do the lion’s share of the marketing. Awareness of the product spreads rapidly from person to person similarly to the way a virus becomes an epidemic. This is distinct from the simple word-of-mouth growth discussed above. Instead, products that exhibit viral growth depend on person-to-person transmission as a necessary consequence of normal product use. Customers are not intentionally acting as evangelists; they are not necessarily trying to spread the word about the product. Growth happens automatically as a side effect of customers using the product. Viruses are not optional.
For example, one of the most famous viral success stories is a company called Hotmail. In 1996, Sabeer Bhatia and Jack Smith launched a new web-based e-mail service that offered customers free accounts. At first, growth was sluggish; with only a small seed investment from the venture capital firm Draper Fisher Jurvetson, the Hotmail team could not afford an extensive marketing campaign. But everything changed when they made one small tweak to the product. They added to the bottom of every single e-mail the message “P.S. Get your free e-mail at Hotmail” along with a clickable link.
Within weeks, that small product change produced massive results. Within six months, Bhatia and Smith had signed up more than 1 million new customers. Five weeks later, they hit the 2 million mark. Eighteen months after launching the service, with 12 million subscribers, they sold the company to Microsoft for $400 million.1
The same phenomenon is at work in Tupperware’s famous “house parties,” in which customers earn commissions by selling the product to their friends and neighbors. Every sales pitch is an opportunity not only to sell Tupperware products but also to persuade other customers to become Tupperware representatives. Tupperware parties are still going strong decades after they started. Many other contemporary companies, such as Pampered Chef (owned by Warren Buffett’s Berkshire Hathaway), Southern Living, and Tastefully Simple, have adopted a similar model successfully.
Like the other engines of growth, the viral engine is powered by a feedback loop that can be quantified. It is called the viral loop, and its speed is determined by a single mathematical term called the viral coefficient. The higher this coefficient is, the faster the product will spread. The viral coefficient measures how many new customers will use a product as a consequence of each new customer who signs up. Put another way, how many friends will each customer bring with him or her? Since each friend is also a new customer, he or she has an opportunity to recruit yet more friends.
For a product with a viral coefficient of 0.1, one in every ten customers will recruit one of his or her friends. This is not a sustainable loop. Imagine that one hundred customers sign up. They will cause ten friends to sign up. Those ten friends will cause one additional person to sign up, but there the loop will fizzle out.
By contrast, a viral loop with a coefficient that is greater than 1.0 will grow exponentially, because each person who signs up will bring, on average, more than one other person with him or her.
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