The result: if you can’t think of ten different things to say, it’s not a problem.  “7 is the magic number, it seems the most comfortable – not exhausting but not incomplete,” writes Jones.  “Perhaps our attention span is shorter than ever?”

“Top 7” lists actually scored a 59% success rate, as measured by Jones, compared to 39% for the traditional Top 10 compilations.  Marketing Pilgrim’s Jordan McCollum, who noticed Jones’s experiment long before I did, also points out that “success” was defined as making the front page of Digg.

Top 12 lists were fairly high achievers, then, registering at a 47% success rate.  “Perhaps 12 feels ‘comprehensive’ and ‘complete,’” suggested Jones.  Top 12 lists were also the longest lists he measured, which leaves me wondering how a 13- or 14-item list would have performed.

How did some other, lower numbers fare?  Well, a Top 3 or Top 4 barely qualifies as a list – don’t bother unless you’re happy with less than a 10% rate of success.  Top 8 lists did even worse, for some reason.   Top 5 and Top 11 lists achieved an equal success rate of 29%.

These statistics could become very useful to Digg users – after all, with 2,500 different pieces in the running, it’s unlikely that one extra-interesting Top 7 list could have skewed Jones’s data set.  But there’s also the theory that measuring something changes it . . .  If a flood of Top 7 lists ensues, don’t expect to see their success continue for long.