Up vote not adding reputation

Let’s say user X has a reputation of 100.
User X has answered a question and has received 0 votes for it. Reputation for user X = 100
after sometime user Y has up voted user X’s answer . Reputation for user X = 110
later after sometime user Z has up voted user X’s answer . Reputation for user X = 110

if a user has received an upvote for an answer, the first time the reputation gets increased.
but if the user already has an upvote for that answer, subsequent upvotes by OTHER users do not affect the answerer’s reputation

Is this by design?