I've been toying with the Books Ngram Viewer at Google Labs. The Ngram Viewer graphs uses of phrases in the Google Books library, which holds about 5.2 million texts, and thus, according to Google, at least, about 4% of all books that have ever been published. There are biases, of course -- very heavy slant toward English language works, and the farther back you go the more difficult the texts to read properly. But it includes text not available to anyone online due to copyright issues. In any case, it's fun to play with. Here's an interesting example, on the relative frequencies of the phrases "every effect has a cause" and "every event has a cause". Click for larger view.)
The Ngram Viewer is case-sensitive, so here's "Every event has a cause" and "Every effect has a cause" (with 'Every' capitalized):
I've talked before about my interest in these two variations; 'event' and 'effect' were originally synonyms, but at some point ceased to be so, and this, I think, has affected a number of philosophical discussions, including discussions of determinism and, of course, causation.