Who typically initiates the topic of exclusivity, or a relationship?

When you're dating someone, who typically initiates the topic of being exclusive, the guy or the girl. And how did you go about doing this? Answer based on your own experiences or the experiences of your friends.
The guy usually initiates it
The girl usually initiates it
Select gender and age to cast your vote:
Who typically initiates the topic of exclusivity, or a relationship?
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