Simple popularity algorithm (using date submitted and # of votes)
<p>I run a digg-like website that promotes content to the front page when it reaches a certain number of votes. Right now it doesn't take date submitted into consideration.</p>

<p>I'd like to use a simple algorithm that just uses the number of votes and the date submitted to determine whether something should be promoted. I don't want the algorithm to do anything more complex then that (such as iterating over all the vote dates).</p>

<p><strong>EDIT:</strong></p>

<p>Shouldn't the formula be something like this:</p>

<pre><code>30 / (days between post date and now) * (vote count) = weighted vote
</code></pre>

<p>Here are some scenarios which seem reasonable for my site, which indicates that the algorithm needs to be more lenient for older items (since older items are less discoverable on the site)</p>

<p>30 / 30 * 30 = 30 (30 days old, promoted with 30 votes)<br/>
30 / 5 * 15 = 90  (5 days old, promoted with 15 votes)<br/>
30 / 1 * 10 = 300 (1 day old, promoted with 10 votes)</p>

<p>How can the formula be modified so the above 3 give close to the same min weighted vote required for promotion?</p>
