3. The number of searches and the number of clicks that your website gets for a certain keyword seem to be considered. Keywords that aren't searched often enough don't get Site links. It also seems that your website has to get many clicks for the searched keyword.
4. The numbers of links that point to your website with the searched keyword as the anchor text seem to influence the creation of Site links. Site links only seem to appear for the main keywords of a website, not for all keywords for which a website is listed.
If your website meets these criteria Google might assign Site links to your website for your most important keywords.
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