The problem with algebra is, it's kinda hard to understand. So let's simplify it. Forget about differentiating your site traffic to discover your growth rate - let's go back to basics with a few thought experiments.
In order to keep it simple, the figures I'll use below are all made up. It doesn't really matter - it's the principles that are important here.
Terminology
First, an indulgence - I'll be using 'c' as shorthand for conversions. As a former Astrophysics undergraduate and associate member of the Institute of Physics, it's an amusement to use the fastest speed there is to represent conversion rate (although physicists would point out that I'm actually using it for total number of conversions, rather than conversion rate).
I'm using n to represent the number of people who search for your target keywords. This has a bearing on how many people you could potentially reach - choose an obscure keyword and there may be nobody searching for it at all.
R is an imaginary way of evaluating search ranking. For simplicity, it scores a page-ten ranking as 0.1, page nine as 0.2 and so on, with a 1.0 score for a page-one listing. Not a foolproof or real-world measure, by any means, but one we can use in our thought experiments.
E is engagement, a similarly imaginary score to help picture how much of a page people read before navigating elsewhere - if your call to action is down the bottom, you'd better hope this figure stays at 100%.
So:
- c is total number of conversions
- n is number of searchers - not number of hits
- R is our ranking weighting - 1.0, 0.9, 0.8 down to 0.1 for a page-ten ranking
- E is the engagement level of our reader - 0.1 up to 1.0 depending on how much of the landing page they read
I'm working on the following assumptions:
- every person who finds your website and is interested will make a purchase
- search ranking is affected by competitiveness of keyword and level of inclusion on the page
- there are no half-measures in R or E - everything is an exact multiple of 0.1
- For every score of '1' you achieve, you get one conversion - one fully engaged reader, two half-engaged readers, and so on.
Raising Rankings
Let's start simple. Search ranking is probably the thing most people are worried about - "let's get on the front page", "where are we in the SERPs?" and all that - and it obviously has an effect.
Using our assumed values above, sliding five pages down the SERPs will halve your total number of conversions, and so on. This one really isn't rocket science.
But it's not the only factor at play - achieving a lower ranking for a more frequently searched query could actually raise your number of site visitors.
Alternatively, target a niche or long-tail keyword and you're in with a much better chance of a front-page listing.
In my case, I might find 'freelance Manchester copywriter' to be too competitive. So I opt for 'freelance Didsbury copywriter' instead.
While n is likely to drop, as much fewer people will be searching for 'freelance Didsbury copywriter', my chances of a front-page ranking are greatly increased. If we're talking about moving from page ten to page one, I can suffer a ten-times decrease in total number of searches and still - according to the God Formula - get as many customers.
Long-tail keywords, though, are by their very nature more specific. So it's fair to assume an increase in your reader's engagement level E. Add this into the imaginary equation and you could arguably see a rise in custom despite targeting a less popular search term.
Raising Engagement
This is not only about the search terms you target - it's also about on-page text. Nobody wants to read a poorly written page full of jammed-in keywords. You might get a better ranking, but your engagement will suffer if it looks like you've written solely with the search spiders in mind.
You can raise engagement simply by being careful about keyword usage. Select grammatical phrases to target - and use Google Trends or a similar keyword tool to research which are actually getting traffic. For me, 'Didsbury copywriter' and 'copywriter Didsbury' may receive the same number of queries, but the latter is almost impossible to place grammatically into a sentence.
Tweaking this variable is about raising E without changing R or n. It's a matter of judgment and, if you get it right, the thing that really differentiates your site as a destination.
Get it wrong and your site is like a closed-down theme park - on the SERPs, like the theme park symbol on a map, it might look good, but once anyone arrives in person it will be nothing but a disappointment.
Increasing n.
Achieving a high 'n' value - the number of people searching for your chosen keywords - is what separates the men from the boys.
There's nothing wrong with being a boy, though. If your business model is best suited to a small crowd of highly engaged searchers, make your money and be satisfied with it.
High 'n' values are for big brands and mass-market products or services. They either require dedicated efforts to reach the top of the SERPs for competitive queries - so that a low R value does not negate the benefit of a large search audience - or a brand name so familiar that people are searching for it specifically, rather than using a generic term.
Many a web-based company has scuppered itself by trying to become a brand. The truth is, you don't need to be a 'destination', it's enough online to simply be 'the best option'. People will find you through searches and your reputation will grow organically.
Particularly in the current age of social networking and user-generated content, allowing positive reviews to emerge and engaging with your customers is arguably wiser than investing in flashy advertising. Many consumers are now too savvy to listen to your opinion of yourself anyway.
Raising Expectations
To summarise, there's really no way you'll ever reach a 100% conversion rate. In addition to the variables outlined above, there are countless others affecting your search ranking, audience size, engagement levels, time on site, geographical coverage, pricing and delivery policies, and so on.
All I have really tried to put across is that, when it comes down to it, tweaking one variable is likely to have a knock-on effect on some or all of the others. The key to long-term success is to be aware of what you are doing at all times and, as the principle of phronesis states, do the right things for the right reasons.