Lately SBD (Steem backed dollars) have been trending on the "Market cap gainers" section on nomics because the price has been pumped on HitBTC.

On coinmarketcap SBD market from HitBTC has been identified as an outlier and ignored from the price calculation.

The pump has been possible only on HitBTC because withdrawals and deposits have been disabled.

If possible, you should ignore markets where withdrawals and deposits are disabled (with exceptions, such as the recent EOS startup). If not practical you should probably make some kind of outlier detection, should not be hard for this example.