Define mig1 rating for municipal bonds?

There are four rating categories for short-term obligations that define an investment grade situation. These are designated Moody's Investment Grade as MIG 1 (best quality) through MIG 4 (adequate quality). Short-term obligations of speculative quality are designated SG. In the case of variable rate demand obligations (VRDOs), a two-component rating is assigned. The first element represents an evaluation of the degree of risk associated with scheduled principal and interest payments, and the other represents an evaluation of the degree of risk associated with the demand feature. The short-term rating assigned to the demand feature of VRDOs is designated as VMIG. When either the long- or short-term aspect of a VRDO is not rated, that piece is designated NR, e.g., Aaa/NR or NR/VMIG 1. Issues or the features associated with MIG or VMIG ratings are identified by date of issue, date of maturity or maturities or rating expiration date and description to distinguish each rating from other ratings. Each rating designation is unique with no implication as to any other similar issue of the same obligor. MIG ratings terminate at the retirement of the obligation while VMIG rating expiration will be a function of each issue's specific structural or credit features. MIG 1/VMIG 1 This designation denotes best quality. There is present strong protection by established cash flows, superior liquidity support or demonstrated broad-based access to the market for refinancing. MIG 2/VMIG 2 This designation denotes high quality. Margins of protection are ample although not so large as in the preceding group.

MIG 3/VMIG 3 This designation denotes favorable quality. All security elements are accounted for but there is lacking the undeniable strength of the preceding grades. Liquidity and cash flow protection may be narrow and market access for refinancing is likely to be less well established.

MIG 4/VMIG 4 This designation denotes adequate quality. Protection commonly regarded as required of an investment security is present and although not distinctly or predominantly speculative, there is specific risk.

SG This designation denotes speculative quality. Debt instruments in this category lack margins of protection.