viral coefficient

Definition

The number of new users each existing user generates through referrals, where anything above 1.0 means exponential growth. It's the mathematical expression of every marketer's fantasy: growth that doesn't require advertising.

Example Usage

Our viral coefficient is 0.3, meaning each user brings in 0.3 new users, which is technically viral if you redefine all the words.

Origin

Borrowed from epidemiology and adapted for startup growth metrics in the mid-2000s

Fun Fact

Hotmail achieved a viral coefficient above 1.0 by simply adding 'P.S. I love you. Get your free email at Hotmail' to every sent message, acquiring 12 million users in 18 months.

Source: Growth marketing and viral marketing terminology

Related Terms

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volubility

The gift of gab taken to professional extremes—someone who talks smoothly, rapidly, and seemingly without ever needing to breathe. In sales and marketing, it's either your greatest asset or most annoying quality, depending on whether you're the one talking or listening. Think used car salesman meets TED talk speaker.

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deck monkey

A junior marketer whose primary job is creating endless PowerPoint presentations for meetings that may never happen. The modern equivalent of a Victorian-era scribe.

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segments

In marketing, the practice of dividing your audience into smaller groups based on demographics, behavior, or psychographics so you can target them with laser precision. It's like organizing your contacts into friend groups, except way more invasive and profitable. The more segments you have, the more you can pretend you understand human behavior.

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ghost bid

A fake bid in programmatic auctions designed to artificially inflate prices without intent to win. The ad tech equivalent of sending your friend to bid up prices at an estate sale.

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click-through

The holy grail metric of online advertising—when someone actually clicks on your ad instead of scrolling past it like the visual noise it usually is. Each click-through represents a tiny victory in the war for attention, though whether that click leads to a sale or immediate regret is another question entirely. Measured as CTR (click-through rate), it's the percentage that determines whether your ad budget was brilliant or wasted.

📣 Marketing / Advertising

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attribution window

The time period during which a conversion can be credited to a specific ad interaction. It's the arbitrary timeframe marketers use to claim credit for sales that may have happened anyway.

📣 Marketing / Advertising

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