The 50% statistic is related to what matters to Google: changes in real search results. It is pretty irrelevant for anybody else. The speed of adding a single

The 50% statistic is related to what matters to Google: changes in real search results. It is pretty irrelevant for anybody else. The speed of adding a single page to the index and updating is, of course, much, much faster (~1000x). I can't parse the measure you propose above.