**the most powerful viral KPI of them all.**Over the course of this adventure, I’ve shown how to increase the potential

**viral magnitude**each user will contribute to your growth (aka your

*K*factor). Based on this, many growth engineers (mistakenly) choose to first focus hard on increasing invites sent per user, their branching factor, and invite conversion rate – all of which go into calculating

**. While these are all worthwhile goals, they will**

*K***NOT**result in the explosive, exponential growth every founder or growth engineer hopes for.

*Okay, okay. Enough of the buildup. What’s this magical, mythical KPI we’re talking about?*I’m glad you asked.

**Viral Cycle Time: The One KPI to Rule Them All**

**Viral cycle time**(which I refer to as

**) is the amount of time between when a new prospective user becomes initially aware of a product and the point where they send out their first invite. To explain how powerful viral cycle time can be, we need to look no further than everyone’s favorite furry forest creature.**

*ct***Why Do Rabbits Have So Many Babies?**

Have you ever had friends pop out multiple children in quick succession and thought to yourself, “*WOW – you guys are like rabbits!*“? I think you might know where I’m going with this.

**Rabbits reproduce very, very rapidly.**So much so that adult rabbits of the opposite sex, if left to their own devices, will likely result in . . . well . . . ABSOLUTE INSANITY. Allow me to elaborate.

**Understanding the Finer Nuances of Rabbit Sex**

*(*

**DISCLAIMER:**I am not a rabbit mating expert. That would be weird. So all my example numbers were taken from a paper published by the University of Miami’s biology department.)**Let’s start with a few assumptions to make our math easier:**

- A single female rabbit has an average litter size of
**six**babies. **Half**of new baby rabbits are female, so**three**new females are produced in each litter.- We’re only discussing reproductive
**capacity**. As such, we will not factor in “*churn*” (i.e. baby rabbits dying for ungodly reasons) OR carrying capacity (i.e. environmental limitations).

**one month gestation period**, and typically produce a half dozen offspring at a time.

*Wowzers*!

**This speeds things up a bit.**What’s more, human females must be a certain age before their bodies actually allow for reproduction. (I believe it’s something like 14 or 15, but don’t quote me on that. I’m a growth engineer, not a doctor.) Female rabbits on the other hand can begin reproducing at

**6 months old.**

*Double wowzers!*If that wasn’t crazy enough, a female rabbit is biologically capable of getting pregnant again within

*minutes*of giving birth. So a female can literally have a new litter every month IF she’s around a totally horny male rabbit (which we’ll assume, for our purposes, she is). So, IF our first female rabbit begins reproducing when she’s of age, and reproduces as frequently as her body is able (AND all new females behave in the same way), I ask you:

**How many actively reproducing female rabbits would we have at the end of each year?**

- YEAR 1: 37 rabbits
- YEAR 2: 1,369 rabbits
- YEAR 3: 50,653 rabbits
- YEAR 4: 1,872,792 rabbits
- YEAR 5: 69,293,304 rabbits
- YEAR 6: 2,563,852,248 rabbits
- YEAR 7: 94,862,569,180 rabbits

**95 billion rabbits**.

**AND THAT’S ONLY THE FEMALES!**IF you add in all the males to that count, we’d have

**184,597,433,860**total rabbits in 7 years.

*That’s very impressive and, if you’re a rabbit, probably reason to celebrate.*

***MIND BLOWN*****What Rabbit Reproduction and Viral Marketing Have in Common**

Two questions remain:
**Well, first off, since rabbits have so many natural predators, their reproductive rate (and more specifically, their reproductive**

*1) How is this even possible?**cycle time*) is their main defense mechanism as a species. However, while its mathematically possible,

**nature wouldn’t allow for this.**Predators would eat a ton of them, food would be too scarce, Elmer Fudd would undoubtedly blow a few away, and a ton of other factors would “

*thin the herd*” to prevent such rapid population growth. (We only went through this to show a real-world example of how the math of viral cycle time works. And talk about rabbit sex.)

**Other than preparing you for the very real possibility of rabbits taking over the world, the point of this whole conversation was to show how something so dramatically explosive could happen (in terms of growth). And to set the stage for how it relates to your virality. The reason rabbits can reproduce at such an alarming rate is NOT because of the size of their litters. Six is a lot from a human perspective, but pretty average in the animal kingdom. Rabbits can reproduce at this rate because of**

*2) Why should I care?***three factors**:

- They can become pregnant very young.
- Their gestation period is very short.
- They can immediately become pregnant again just minutes after giving birth.

**cycle time.**

**Getting Back to Business**

Many engineers, marketers, and founders with a bit of viral knowledge choose to focus more on optimizing their viral factor (**) to max out invites per user (i.e. trying to get each rabbit to have 8 babies instead of 6). However, reducing viral cycle time (i.e. reducing a rabbit’s gestation period from 30 days to 20 days) is**

*K***MUCH**more impactful. To explain, let’s look at a basic equation:

*x^y**(If you’ve never seen the “*Now, here are two options. Pick the one you think will result in the larger number:

**^**” symbol before, it denotes exponentiation. So another way to state this equation would be**x to the power of y**.)- Add another
to give you**x****(x * 2)^y** - Add another
to give you**y****x^(y * 2)**

**Not so fast.**I want you to be absolutely certain, so I’ll elaborate:

- Let’s say
is your invites sent per user (**x**) – or how many new users an existing user will spread your product to per cycle.*i* - Let’s then say
is the number of cycles that take place within a certain time period – which is your viral cycle time (**y**).*ct*

*x*and have a cycle that spreads to 10 people (x = 10) but takes 7 days to replicate, in 4 weeks (y = 4) you’ll have

**10^4**, which equals

**10,000**. If you INSTEAD focus on cycle time, and you spread only to 3 people (x = 3) but it only takes 1 day to replicate, in 4 weeks (y = 28) you’ll have

**3^28**, which equals

**22.8 TRILLION!**That’s some impressive exponential growth. Once you’ve achieved a stable, strong viral factor, you can achieve this same type of cataclysmic viral awesomeness by reducing your cycle time. Here’s what that looks like in exciting graph form: The ultra-simplistic model above tells us that trying to achieve a faster cycle time (

*ct)*is a

**FAR**more impactful change than improving how many invites your users send (

*i*

*)*.

**What’s Next**

This model, red line and all, is far too simple for real, practical use.
Due to the fact that there’s zero loss (i.e. baby rabbits dying) or saturation in terms of what’s being factored in here, our scenario has no basis in reality. It’s just an example of how much more of an impact one KPI can make over an another.
To get you some real, practical value to help your product spread, let’s head on over to the next chapter, shall well?
## Want to Dramatically Effect Your Growth By Reducing Cycle Time?

Rabbits are cute and all, and reproduce almost as much as the Kardashians, but to really relate them to viral marketing we need to introduce some drama. Ever hear the fable about

*The Snail and the Hare*. You’re about to.Latest posts by Travis Steffen (see all)

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