Breaking Down The Three Engines Of Growth

As Eric Ries specified in an article entitled “The Law of Sustainable Growth,” as an extract of The Lean Startup:

The engine of growth is the mechanism that startups use to achieve sustainable growth. I use the word sustainable to exclude all one-time activities that generate a surge of customers but have no long-term impact, such as a single advertisement or a publicity stunt that might be used to jump-start growth but could not sustain that growth for the long term.


What is sustainable growth for a startup?

In the same article, Eric Ries defined sustainable growth:

Sustainable growth is characterized by one simple rule:

New customers come from the actions of past customers.

Like in a feedback loop triggered by network effects, the actions of past customers need to drive new customers, with more speed and efficiency.

How do customers drive sustainable growth?

Eric Ries classified the ways customers drive sustainable growth as falling into four primary categories:

  • Word of mouth: those are usually triggered by “customers’ enthusiasm for the product.”
  • As a side effect of product usage: this is usually true for viral products, those that enable network effects to pick up over time.
  • Through funded advertising (paid advertising)
  • Through repeat purchase or use (driving the repeat customer)

As Eric Ries points out those sources of growthpower feedback loops that I (Eric Ries) have termed engines of growth.

The three engines of growth

Eric Ries breaks down the sustainable growth in three key drivers:

  • The sticky engine
  • The viral engine
  • And the paid engine

The Sticky Engine of Growth

Through this engine, you want to focus on making sure your customers go back to use your product or service. You might want to answer questions such as: are users returning? Are they engaging? A low stickiness of the product entails a high churn rate. And in many cases, according to the lean startup if you’re a product isn’t engaging it’s tough it will be successful in the long-run.

What are the key metrics to measure stickiness?

Some of the key performance indicators (KPI) for stickiness are customer retention metrics measured in:

  • Churn rates
  • Usage frequency
  • Customer retention rate
  • Customer acquisition rate

The Viral Engine of Growth

Word of mouth and virality can substantially lower the marketing costs associated with growing a users’ base. That is why, for many startups, that is seen as a key element for growth.

At its core virality implies that each customer brings in more than one person that becomes a paying customer to your business. Thus, when new users bring in more new users, that enables a compounding effect.

What’s the key metrics to measure virality?

When a user invites more than a friend to join your platform, that means your viral coefficient is higher than one. The viral coefficient is the key metric to track to understand viral growth.

The Paid Engine of Growth

The paid engine usually kicks in once stickiness and virality have picked up. Otherwise, spending might be extremely inefficient, thus making the company lose money on its attempt to acquire paid customers.

What’s the key metrics to measure virality?

The paid engine has two key metrics:

  • Customer lifetime value
  • Cost per acquisition

When the customer lifetime value is higher than the acquisition cost, the company has figured out how to make money through the paid engine.

Key Takeaways

  • The Engine of Growth: The mechanism startups use to achieve sustainable growth, excluding one-time activities, and focusing on continuous and long-term impact.
  • Sustainable Growth for a Startup: New customers come from the actions of past customers, creating a feedback loop that drives growth with more speed and efficiency.
  • Ways Customers Drive Sustainable Growth: Customers contribute to sustainable growth through word of mouth, as a side effect of product usage (viral effects), funded advertising, and repeat purchases or use.
  • The Three Engines of Growth:
    • The Sticky Engine of Growth: Focuses on ensuring customers regularly use the product or service. Key metrics include churn rates, usage frequency, customer retention rate, and customer acquisition rate.
    • The Viral Engine of Growth: Leverages word of mouth and virality to attract new customers. Key metric is the viral coefficient, indicating if each customer brings in more than one new paying customer.
    • The Paid Engine of Growth: Comes into play after stickiness and virality have picked up. Key metrics are customer lifetime value and cost per acquisition to determine profitability.

Read Next: Business Model Innovation, Business Models.

Related Innovation Frameworks

Business Engineering


Business Model Innovation

Business model innovation is about increasing the success of an organization with existing products and technologies by crafting a compelling value proposition able to propel a new business model to scale up customers and create a lasting competitive advantage. And it all starts by mastering the key customers.

Innovation Theory

The innovation loop is a methodology/framework derived from the Bell Labs, which produced innovation at scale throughout the 20th century. They learned how to leverage a hybrid innovation management model based on science, invention, engineering, and manufacturing at scale. By leveraging individual genius, creativity, and small/large groups.

Types of Innovation

According to how well defined is the problem and how well defined the domain, we have four main types of innovations: basic research (problem and domain or not well defined); breakthrough innovation (domain is not well defined, the problem is well defined); sustaining innovation (both problem and domain are well defined); and disruptive innovation (domain is well defined, the problem is not well defined).

Continuous Innovation

That is a process that requires a continuous feedback loop to develop a valuable product and build a viable business model. Continuous innovation is a mindset where products and services are designed and delivered to tune them around the customers’ problem and not the technical solution of its founders.

Disruptive Innovation

Disruptive innovation as a term was first described by Clayton M. Christensen, an American academic and business consultant whom The Economist called “the most influential management thinker of his time.” Disruptive innovation describes the process by which a product or service takes hold at the bottom of a market and eventually displaces established competitors, products, firms, or alliances.

Business Competition

In a business world driven by technology and digitalization, competition is much more fluid, as innovation becomes a bottom-up approach that can come from anywhere. Thus, making it much harder to define the boundaries of existing markets. Therefore, a proper business competition analysis looks at customer, technology, distribution, and financial model overlaps. While at the same time looking at future potential intersections among industries that in the short-term seem unrelated.

Technological Modeling

Technological modeling is a discipline to provide the basis for companies to sustain innovation, thus developing incremental products. While also looking at breakthrough innovative products that can pave the way for long-term success. In a sort of Barbell Strategy, technological modeling suggests having a two-sided approach, on the one hand, to keep sustaining continuous innovation as a core part of the business model. On the other hand, it places bets on future developments that have the potential to break through and take a leap forward.

Diffusion of Innovation

Sociologist E.M Rogers developed the Diffusion of Innovation Theory in 1962 with the premise that with enough time, tech products are adopted by wider society as a whole. People adopting those technologies are divided according to their psychologic profiles in five groups: innovators, early adopters, early majority, late majority, and laggards.

Frugal Innovation

In the TED talk entitled “creative problem-solving in the face of extreme limits” Navi Radjou defined frugal innovation as “the ability to create more economic and social value using fewer resources. Frugal innovation is not about making do; it’s about making things better.” Indian people call it Jugaad, a Hindi word that means finding inexpensive solutions based on existing scarce resources to solve problems smartly.

Constructive Disruption

A consumer brand company like Procter & Gamble (P&G) defines “Constructive Disruption” as: a willingness to change, adapt, and create new trends and technologies that will shape our industry for the future. According to P&G, it moves around four pillars: lean innovation, brand building, supply chain, and digitalization & data analytics.

Growth Matrix

In the FourWeekMBA growth matrix, you can apply growth for existing customers by tackling the same problems (gain mode). Or by tackling existing problems, for new customers (expand mode). Or by tackling new problems for existing customers (extend mode). Or perhaps by tackling whole new problems for new customers (reinvent mode).

Innovation Funnel

An innovation funnel is a tool or process ensuring only the best ideas are executed. In a metaphorical sense, the funnel screens innovative ideas for viability so that only the best products, processes, or business models are launched to the market. An innovation funnel provides a framework for the screening and testing of innovative ideas for viability.

Idea Generation


Design Thinking

Tim Brown, Executive Chair of IDEO, defined design thinking as “a human-centered approach to innovation that draws from the designer’s toolkit to integrate the needs of people, the possibilities of technology, and the requirements for business success.” Therefore, desirability, feasibility, and viability are balanced to solve critical problems.

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