real national tiers based on facts

If you're basing on established history and historical impact, reputation across the majority of the country at LARGE campuses, sisterhood, philanthropy, popularity (# of active chapters, active members, and alum), I'd go more like this (in no particular order within tier):

(If I can find the data, I’m including #’s for active members in 2017, # members initiated lifetime, and active chapters)

Top:
ΧΩ (~20,000 / ~330,000 / 181)
ΔΓ (~15,000 / ~250,000 / 150)
ΚΚΓ (~260,000 / 140)
ΚΑΘ (~20,000 / ~270,000 / 143)
ΠΒΦ (~300,000 / 138)
ΔΔΔ (~17,000 / ~200,000 / 141)

Almost Top:
ΖΤΑ (~245,000 / 169)
ΚΔ (~14,000 / ~230,000 / 165)
ΑΦ (~200,000 / 170)

Solid Mid:
ΑΔΠ (~220,000 / 155)
ΦΜ (~185,000 / 123)
ΑΧΩ (~200,000 / 193 including inactive)
ΓΦΒ (~200,000 / 187 including inactive)
ΣΚ (~165,000 / 124)
ΑΟΠ (~14,000 / ~190,000 / 143)
ΑΞΔ (~175,000 / 130)
ΑΓΔ (~170,000 / 112)
ΔΖ (~244,000 / 165)

Lower Mid:
ΣΣΣ (~125,000 / 112)
ΑΣΑ (~125,000 / 85)
ΔΦΕ (~67,000 / 105)
ΦΣΣ (~60,000 / 115)

Low:
ΑΕΦ (~80,000 / 50)
ΑΣΤ (90)
ΘΦΑ (58)
ΣΔΤ (~60,000 / 64)


Keep in mind Greek Life is MORE than just large D1 universities. The lower mid and low groups I classified as such because they're newer to NPC, and primarily stick to smaller and/or private campuses. A Phi's strong popularity outside of the west coast is fairly new, so they don't get to be top just yet. But if they keep this up, in another 20 years they will be. Zeta and KD could very well be top, I could be convinced of that. But A Phi still isn’t quite there yet, but they’re way more than a mid tier.