Interesting Finding in Temporal Analysis of text

I found the following graph very interesting. The graph shows usage pattern of two English words "however" and "However" from 1800 to 2000. Note that "however" (small h) is used in the middle of sentence where as "However" (Capital H) is used at the beginning of a sentence.

Source: datamining.typepad.com

datamining.typepad.com : How do we interpret this? The most obvious interpretation might be that 'however' at the beginning of a sentence is becoming more frequent. We could also conclude that 'however' in general is becoming more frequent (imagine if we could combine the lines). Alternatively, it could mean that sentence length in the corpus is shifting. Given that we don't know the exact cultural mix of the 'British English' corpus, it could be somehow related to the mixture of American and British content. Finally, it could be due to the mix of fiction and non-fiction. Interestingly, the 'American English' corpus has quite a different signal.