The following quotation is taken from Hywel Jones' chapter "Preaching sola fide Better," in Covenant, Justification and Pastoral Ministry (ed. R. Scott Clark).
"Only a fraction of the present body of confessing Christians are solidly appropriating the justifying work of Christ in their lives. Many have so light an apprehension of God's holiness and of the extent and guilt for their sin that consciously they see little need for justification, although below the surface they are deeply guilt ridden and insecure.
Many others have a theoretical commitment to this doctrine, but in their day to day existence they rely on their sanctification for justification drawing their assurance of acceptance with God from their sincerity, their past experience of conversion, their recent religious performance or the relative infrequency of their conscious, willful disobedience.
Few know enough to start each day with a thoroughgoing stand on Luther's platform; you are accepted, looking outward in faith and claiming the wholly alien righteousness of Christ as the only ground for acceptance, relaxing in the quality of trust which will produce increasing sanctification as faith is active in love and gratitude."
Richard Lovelace, cited in CJPM, p. 310-11
I suspect that this description, anecdotal and general rather than scientific, is pretty accurate. The cause of it may well be ignorance and lack of teaching, rather than willful resistance to the truth of justification by faith alone. Or it may be a failure of applying the truth of justification by faith alone (which in itself highlights a deficient grasp of the doctrine). Nonetheless there is always a price to pay when error fills the space that truth is meant to fill. And error is never a merely intellectual matter. Error does damage to our capacity to live before God and others as he wills that we should.