"Diversity" is measured by FICO in the category called "Types of Credit," which comprises, on an average, approx 10% of total score.
The percentage varies between individual consumers based on the scoring segment, or "bucket," categorization of their overall credit file, so view of your credit file "diversity" will vary over time, depending upon your scoring bucket.
Types of credit, in my reading of experiences posted by others, places primary emphasis on the showing of effective use of discretionary, revolving credit. FICO places strong emphasis on evaluating risk of future delinquency based on focus on revolving credit, as it is usually the first indicator of potential consumer distress. Stated stimply, a consumer is most likely, when $$ gets short, to first pay their mortgage and auto, so they are not usually the first indicators of risk. Consumers cannot, at their discretion, increase their installment debt obligations without a new account agreement, which requires re-evaluation of their currrent credit history. However, consumers can, at their discretion, increase debt up to their currently approved credit limits on revolving accounts. So an undisciplined consumer can increase debt without creditor evaluation up to those limits.
From my readings, I would assume that use of revolving credit is somewhere around 90% of evaluation of types of credit, and installment checks in at approx 10%.
My guess, but I think it is pretty certain that the split is weighed heavily towards revolving. At 10% of scoring, total types of credit would only be 85 points. If one assumes a 90/10 split, installment would check in at less than 10 points. Many post great scores here on the site with no installment accounts.
Being able to manage two or more discretionary, revolving lines of credit shows more consumer reliability, so it appears that FICO rewards for multiple revolving, but of course, up to a limit. It appears that three is around ideal, with declining benefit thereafter. The quality of the revolving accounts, such as store vs. bank cards, secured vs unsecured, etc., also seems to figure in the mix, but to what level, I am unsure.
Thus, my view of diversity is to have 2-4 revolving, preferably unsecured and major bank cards, and then lower in importance, an installment loan or two.
