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Thursday 12 October 2017

The half-life of a link is two year

The half-life of a link is two year. Better said, the half-life of an external link is two year. 

That is, when you create today a website with 100 working external links and checks your website after two year with a broken link checker, you will discover that rougly 50 links are broken.

How do you know?

I can almost hear you thinking "How do you know?". Well I will explain below.

In the past I have copied as much data as possible of the directory Yahoo! This is because Yahoo! stopped, I have created a directory myself and I wanted to analyse the links and structure of this famous directory.

At January 4, 2016 I analysed the data I have and concluded that 77% (or more exactly 76.8387682%) of the links are fine.

Recently (October, 9 2017) I analysed the data again. Now 42% (42.0219319%) of the links are fine.

Based on this data I concluded that on an average day 0,093670021% of external links will get broken. That does not seem much. However the linkrot percentage per month is 2.81%. 


After a half year one sixth of the links are broken.
After a year 30% of the links are broken.
After two years 50% of the links are broken. Hence the half-life of a link is two year.

See also this graph below

So when you think 3% broken links is acceptable, then you should check for broken links every month.

When 5% is acceptable, check every two months and when you think 10% is acceptable, check every 4 months for broken links.

Tip: Use the tool Maintenance Frequency at a Glance to find your optimal maintenance frequency. 

Be wise, and check and repair your links at a regular base,

Update: After writing this blogpost  I discovered that in the document "A longitudinal study of Web pages continued: a consideration of document persistence" it is stated that the half-time of a random web page is about 2.0 years. Great that's exactly what I concluded.  

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