How much legit is a referral or downline builder program?

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whenever we join a PTC site the need for referrals hits our mind as it is the only way to earn a decent cash from PTC sites rather than just hitting for pennies. There are many sites which claim to build downline or active direct referrals for free or for some money but i have not seen any kind of progress in referrals with such programs. Some of my friends have been using the PTC sites & referral builder sites with a 0% to 1% referral growth. Are there any genuine sites that really make a downline or is it just another scam on internet.