Deductor always think about the TDS Rates. Deductor deduct TDS on behalf of Income Tax Department and deposit the same accordingly. But there is fear regarding change of TDS rates.
In case TDS rates have been reduced and deductor deduct / deposit higher rates (as earlier applicable) then Income Tax department has no problem. In other side in case TDS rates goes on higher side and deductor deduct / deposit lower rate (as earlier applicable) then Income Tax department raises demand notice to deductor that you have not deducted TDS accordingly to TDS rates and you have to deposit the balance TDS with Interest.
However Deductor should read below TDS Rates before deducting TDS for the Financial Year 2015-16 or Assessment Year 2016-17
to view the table of TDS Rates. (Official Link)