If new purchases are triggered by old purchases, the doubling time depends on bank's speed. In April it was wire to Gox, which took several days, now it is transfers to btcchina, which is instant.
wires into Gox take around 2 weeks at the moment.
1) Currently Gox promise 11 working days, but deliver for 6.
2) But current Gox speed doesn't matter because we are comparing
April's Gox with today's btcChina.