None of the legal periodical indexes are comprehensive, but I do wonder why it's necessary to be deliberately non-comprehensive. I'm referring to the situation when Index to Legal Periodicals decides to add a new journal. Take the example of Albany Law Journal of Science & Technology, coverage is:
Index to Legal Periodicals: v9 (1999)-
Legal Resource Index: v1 (1991)-
Westlaw (complete full-text): v2 (1992)-
Lexis (complete full-text): v4 (1994)-
When ILP added the journal it chose not to index vols 1-8, which can certainly be understood in terms of the printed volumes, but when (I'd hazard) the majority of searches in ILP are done online it makes poor sense not to go to the trouble of back-indexing. Surely if vol. 9 is of value, then vol. 8 is too. ILP just shows up as being much the least adequate in coverage. Creating a more comprehensive database version than print version also offers H.W. Wilson the possibility of recompiling the print source and re-selling it to law libraries!