Your response rate is the calculated on two things: it is the percentage of new conversations and exchange proposals to which you've responded. For messages, only the very first message sent to you in a conversation counts toward your exchange rate to avoid an endless loop. Any subsequent messages or responses do not count. When someone starts a new conversation with you, you are given 3 days to respond before it counts against your response rate. If you respond within that time, it is counted immediately. Only conversations that were started by someone else will count in your response rate. If you started the conversation, it will not count. Only conversations started by Premium members count. Consider also that a message deleted without response will count forever against your exchange rate. Contact support if you have no visible messages without response but your response rate is not 100%.