[R] VIF estimation in R

[Brian Smith]

I have below model

library(car)

data(Duncan)
vif(lm(prestige ~ income + education - 1, data=Duncan))

With this, I am getting a warning message

Warning message:

In vif.default(lm(prestige ~ income + education - 1, data = Duncan)) :

  No intercept: vifs may not be sensible.


Why for model with no intercept, vifs may not be sensible?