We’ve already touched on some of the higher-level viral KPIs, but we haven’t yet dove deeply into 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 K.

While these are all worthwhile goals, they will 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 ct) 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.

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).

For context, while human mothers have a 9+ month gestation period before birthing one (or very occasionally a few) offspring, rabbits have a 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

You probably assumed that it would be quite a few. But you probably didn’t realize that after 7 years you’d have almost 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. *MIND BLOWN*

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

What Rabbit Reproduction and Viral Marketing Have in Common

Two questions remain:

1) How is this even possible?

Well, first off, since rabbits have so many natural predators, their reproductive rate (and more specifically, their reproductive 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.)

2) Why should I care? 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).

To set the stage for how it relates to your viral potential - 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 three factors:

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

To sum up, the reproductive habits of rabbits mirror viral growth, and that growth is so insane because they have a very fast 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 ( K) 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 MUCH more impactful. To explain, let’s look at a basic equation: x^y (If you’ve never seen the “^” symbol before, it denotes exponentiation.

So another way to state this equation would be x to the power of y.) Now, here are two options. Pick the one you think will result in the larger number:

1. Add another x to give you (x * 2)^y
2. Add another y to give you x^(y * 2)

Option 2 is the winner, right? Not so fast. I want you to be absolutely certain, so I’ll elaborate:

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

If you work hard to increase 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.

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