WARNING: Scientific content.

I now have actual real-world numbers that prove a site redesign can more than double the organic traffic to your website.  That means higher visibility in search engines and reaching more customers.  The website was one I'd done years ago and the design as well as the search engine optimization were well outdated.  The first thing I did was get the old site on Google Analytics while I did the redesign, and got a six-month collection of baseline data.  I was asperimentin.

The best part is that all other variables stayed the same, so this increase is entirely due to my recent redesign, as that's the only difference.

The numbers here are the two date ranges.  The 'organic' numbers are people coming to the site through search engines, and higher numbers mean the site is placing higher in search results.  The direct numbers are people typing in the URL directly, so they've either heard the address in an existing radio spot or piece of literature, or used a bookmark to the site.  

The other referrals are links from other sites, and those more or less track those sites' traffic rates (so if they go down it's probably because those sites didn't have as much traffic).  The inbound links and direct traffic are the control group, which wouldn't change because I redesigned the site.  The organic traffic is a direct result of redesigning the site.

The percentages are the percent of total traffic.  You can see that even though Yahoo had a much higher increase, it's only six percent of the total traffic.  But Google went from twenty to forty percent of the total traffic, a 150% increase.  In your face, Yahoo!

The other new statistic was that the site now gets 20% more traffic overall since the redesign.  Since the direct traffic actually went down, that means that the redesign more than made up for the decrease in direct and referral traffic.

If you're reading this and your website is more than two years old, you should consider getting it updated.  In internet time, that's like 50 years.