The number of bitcoins mined each day is a very small fraction of the supply of bitcoins at exchanges. Miners have very little effect (if any) on the bitcoin exchange rate.
Currently it is still large, will get less after another 2-3 reward halving, my estimation of daily coin supply is 5000 - 6000 coins. Short term speculation not included
Although the exchange handle hundreds of thousands of volume of transaction, the added coin supply mostly come from mining, all the existing holders can only dump their coins for once, and they don't have the motivation to dump more than 10% of their holdings per year
The total volume of bitcoins traded daily averages about 160K. The total volume of bitcoins mined daily averages more than 3600 (it depends on the rate of increase of hash rate), but currently it is about 4500.
That's about 3% of total volume, and it assumes that all mined coins are sold. My guess is that newly mined coins only make up about 1% of total trading volume and I consider that to be very small, especially considering the volatility of trading volume.