SEO statistics: Predicting traffic growth

Ian Lurie

Prospective clients always want to know: What kind of impact will SEO have? How much traffic will I get?

I’m an empirical guy. I want to give an answer. But based on what?

Well, I did some serious digging into traffic patterns over time across 200 Portent clients, and I have some answers. Warning: This data heads into seriously touchy-feely statistics. Use with caution.

Oh, and I refuse to make an infographic.

Where the data came from

I pulled data as follows:

  • 75% from Google Analytics, via the API.
  • 15% from historical reports
  • 10% from other analytics tools, like WebTrends

For all data, I used the last day of the month as that month’s result. So month 1 traffic data is what the client saw after a full month of SEO.

With balanced SEO, the first month rocks

Clients working on both on- and off-site SEO saw the biggest percentage growth the first month—over 100% rise in non-branded organic traffic. But overall growth stayed strong and continued to rise over six months. Overall results? 300% growth.


A SEO balanced approach shows 300% growth over 6 months

‘Non-branded organic traffic’ means traffic from natural search results, not including queries on the clients’ brand names.

Geekery: Some big differences

When I went through the data, though, I noticed a lot of outliers:

  • Clients who had huge jumps and drops in traffic that couldn’t be explained by seasonality.
  • Clients who got amazing results. One saw a 2200% increase in two months.

If you’re a statistics geek, month 1 saw deviation of 2.4. Ouch. In non-nerd terms, that’s like aiming for New York and having a good chance of missing the city and the planet, and landing in the Sun by mistake.

After month 1, the deviation drops fast: .4 deviation in month 2, then .3 in month 3, then .12. For month 6, the statistical gods gave me the finger: Deviation shot back up to .24. Which, if I were aiming for New York, would put me in the Pacific Ocean. Probably somewhere shark-infested.

Still, none of this made me super-confident. My data seemed to show there was no pattern, at all.

Then I started pulling things apart a little, and it made more sense.

All onsite, no offsite SEO means fast, brief growth

Clients who let us do onsite SEO but skipped offsite for one reason or another showed big initial growth, then a fast drop off to nothing:

Live by onsite, die by onsite. Onsite SEO is a good short-term builder.

Live by onsite, die by onsite. Onsite SEO is a good short-term builder.

That doesn’t mean onsite SEO is only worth doing for two months, by the way. Stop doing onsite SEO, and problems creep back in, you drop out of the rankings, and traffic goes down again. That’s not a statistic—that’s Uncle Ian’s School of SEO Hard Knocks.

What these numbers really show is that onsite SEO is about an initial sprint, and then maintenance: Hard, ongoing work to preserve the gains you’ve made if, say, the development team decides to rebuild the whole site using javascript and Flash, or the CEO wants the home page to be one big image and the word “BUY”.

I’d love to do a chart of folks who stopped doing onsite, but most of them don’t want me to have their data. Can’t imagine why.

All offsite, no onsite: A long, slow slog

We’ve also had clients over the years who only let us do offsite SEO. The results, if we stick as close to white-hat link acquisition methods as humanly possible, aren’t that exciting:

Offsite SEO has long term prospects but little short-term results

Offsite SEO has long term prospects but little short-term results

Not shocking. If all you do is offsite SEO—guest blogging, link bait, link detective work and such—you pick up momentum, but it takes time. It also keeps paying off, by the way, forever.

Offsite’s a little difficult to attribute. Part of offsite is writing onsite content. That could, theoretically, impact onsite SEO as well. So I only picked sites that were utter onsite catastrophes, where I knew the relevance impact of new content would be zilch.

The balanced approach wins

When I analyzed the balanced data minus the just-offsite or just-onsite SEO crowd, the results stuck, and the deviation numbers were far lower. So I’m willing to stick with this version:


A SEO balanced approach shows 300% growth over 6 months


SEO pays off big over time. It may pay off big, fast, but that depends on your team, your site, and the resources available. I’ll revisit this data periodically and see how the numbers change. For now, I’ll be keeping this around as a general guideline that I follow with lots of disclaimers.

Please don’t go stake your career on these graphs. I have a BA in History and a JD. My qualifications as a mathematician are purely genetic. Plus, I have enough guilt in my life.

Side note: Why only 6 months?

I picked six months as the timeframe for three reasons:

  • After six months, there’s great growth, but the numbers diverge more and more as some clients stick with it and others stop.
  • Average client tenure at Portent is 3 years, but some clients are with us on a short-term consulting basis of six months or less. I could get the biggest dataset with a 6-month timeframe.
  • I got tired.
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  1. Great post, these numbers are very close to what is the trend of our clients too, faster growth at the beginning due to the growth in terms of links and optimised pages, then a slowdown for 2-3 month, then they start ranking for the big month 4-6 month in. This is also a matter of frequency and quality of content update I noticed.

    1. Good to know. If anyone else can add their observations, it’d help a lot – I’m still not totally confident in my analysis.

      1. Another thing that’s important is how much traffic and SEO the client has already done. These stats to me apply only if they didn’t do much seo earlier or if the traffic numbers are not very high already. We have clients coming to us with 2-5 million uniques/month, reaching 15 million obviously takes more than 6 month.

        1. Yeah our average client in this study started at 15-20,000 organic uniques per month, and had at least one ‘deal breaking’ SEO issue. In my experience, most of them do. But it totally depends on your client base.

  2. Thank you for not creating an infographic. Talk about beating a dead horse then shooting it with a bazooka.
    It’s interesting how the growth slows down for off-site SEO in months 3-4 – is this a factor of the links aging or being indexed slowly? In any case, it’ll be something that I keep in mind when I communicate with clients who keep wanting “instant results.”

    1. No, it’s just the nature of the work. The first month is the fluke – it’s usually huge because there are onsite issues we can quickly fix. When those are fixed, you get an instant boost. After that, it’s a more gradual process.

      1. Ian,
        How do you manage a new client’s expectation? Do you let the client know that the first month is usually a fluke and that the SEO process is more gradual afterwards?

  3. Thanks for these data. Did you also investigate the % of traffic that wbes receive depending on their position on the results page? The two pieces of research I use, predict either 12% or 32% for the % of traffic a webs gets being plced first in SERPs.
    Thanks in advance,
    René de Jong
    CEO Internet Advantage

    1. I rely on Slingshot SEO’s research as far as clickthru. It’s pretty conservative, with only 16% or so from #1, but it’s good for expectation-setting.

  4. The first month is always a great boost, but on long term clients we also tend to pour way more time into it. It’s not that it’s the time = results but more that we need to get to grips with the client and understand their business.
    But, the first month boost from fixing the obvious soon turns into the real work which is the long, gradual polishing, content development and link building that really gets them established.
    Great post though, can’t beat statistics when you are telling people what to expect long term (to stop them running off for another ‘first month boost’ with another SEO company)

  5. Hi – Can anyone please help me find out keywords listed under “(NOT Provide)” category in GA. This is hampering my progress to show clients how much traffic each keywords is generating!

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