Sounds about right. Like I mentioned, 1-5 years is normal, but anything above is usually the extreme.
people like to be within a similar age bracket.
Women do on average always date older, but like you said it's almost always < 5 age difference.
reason? Maturity, established bank accounts, career and toys < Biggest reason (finances)
A 21 year old women would almost always rather lock down a 25 year old who's career bound, then some 21 year still smoking weed in his single bedroom room that's shared with his parents. Most people over 25 have there own flat, reliable source of transportation and are within entry level positions.