I see that CK considers a good number of active accounts to be 21+ So does the number of accounts really affect credit score?
Lets say I have 3 credit cards and no other history and always pay in full. If my friend had 5 cards and had the exact same everything as me except number of cards, would his score be better than mine after one year?
@creditconcept wrote:I see that CK considers a good number of active accounts to be 21+ So does the number of accounts really affect credit score?
Lets say I have 3 credit cards and no other history and always pay in full. If my friend had 5 cards and had the exact same everything as me except number of cards, would his score be better than mine after one year?
CK uses a reverse looking premise: high scoring credit people in their algorithm have generally been using credit for a while and therefore have lots of accounts on their record. It's a sloppy analysis frankly, using results to generate the data... even if I once did that in a lower division Physics lab myself 
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FICO doesn't really care, anything beyond 3 revolving accounts appears to be pretty moot from a scoring perspective. You might build up payment history a little faster if we're talking building out of no/thin file situations, but there's massive diminishing returns all over the algorithm.
I would state that you want at least 4 tradelines active, and at least 3 of those should be revolving accounts (hard to do less than half reporting a balance with less than that); this measurement though is more from an underwriting perspective as the classical definition of thin file is <4 accounts by most standards, even 2 credit cards is all that's really "needed" to get to 760+, but I'd suggest it's a quicker walk with a few more cards and also an installment loan or two.
ETA: I'd love if we ever got the chance to do that sort of testing as you suggest - maybe if I ever have kids when they turn 18 I'll use them as lab rats hahaha.
