Can anybody tell me the usually increase of difficulty for btc? is it 20 percent every 2 weeks?
prediction for next diff change or the ones after that is impossible
here you have a simple site showing history and predictions according to calculations (variables as block times and network hash power changes constantly)
https://bitcoinwisdom.com/bitcoin/difficultySo far the last two have been very low, could've been even a lowering of the difficulty, this round it's again slightly up.
Since the drop of BTC a lot of hardware has been switched off or replaced with other equipment.
What comes to this round you can not predict it yet... still 12.6 days to go on this round and anything can happen during that time.