Why you start the bull market in April 2011 and not earlier? The chart shows very bullish movements before April 2011.
I'll answer since this is the chart I also draw - because Gox opened in April (it existed before that, but really opened for wires and trading BTC only in March/April 2011). Before that, there was no significant trading volume, besides some OTC deals, which, without an established price, were mostly noise. It makes sense to discard noise.