Ripple can flood the market with XRPs
Ripple escrowed 55 billlion XRP for Supply Predictability. The escrowed XRP cannot be touched and thus is not part of the circulating XRP supply, just as not yet mined BTC isn't part of the BTC supply.
Ripple is transparent about the XRP they possess in their quarterly reports:
We use Escrow to establish 55 contracts of 1 billion XRP each that will expire on the first day of every month from months 0 to 54. As each contract expires, the XRP will become available for Ripple’s use. You can expect us to continue to use XRP for incentives to market makers who offer tighter spreads for payments and selling XRP to institutional investors.
We’ll then return whatever is unused at the end of each month to the back of the escrow rotation. For example, if 500M XRP remain unspent at the end of the first month, those 500M XRP will be placed into a new escrow account set to expire in month 55. For comparison, Ripple has sold on average 300M XRP per month for the past 18 months.
Check https://ledger.exposed for live statistics about XRP distribution.
Read more about the effect XRP sales from Ripple has on the XRP price in the Q1 2018 rapport
Check this article for an educating read 🎉