1. A non-transitory storage medium storing instructions readable and executable by an electronic data processing device to perform a method operating on an ARPA table for a modeled natural language in which each entry of the ARPA table includes an n-gram Az, an associated backoff value Az.p equal to the conditional probability p(z|A) that symbol z follows context A in the modeled natural language, and an associated backoff weight value Az.b for the context A, the method comprising: computing by said electronic data processing device a max-ARPA table from the ARPA table by operations including: computing and adding for each entry of the ARPA table an associated maximum backoff weight product value Az.m wherein the computing and adding of the associated maximum backoff weight product values is performed on the entries of the ARPA table in descending n-gram order; and after computing and adding the associated maximum backoff weight product values, computing and adding for each entry of the ARPA table an associated max-backoff value Az.w=w(A,z) where w(A,z)=max h p(z|hA) is the maximum backoff value for any head h preceding the context A of the n-gram Az and the computing and adding of the associated max-backoff values is performed on the entries of the ARPA table in descending n-gram order; wherein each entry of the max-ARPA table includes an n-gram Az and its associated backoff value Az.p, backoff weight value Az.b, maximum backoff weight product value Az.m, and max-backoff value Az.w: and computing by said electronic data processing device a max-backoff value w(A,z) for an n-gram Az of the modeled natural language that is not in the ARPA table by applying the recursive equation: w ⁡ ( A , z ) = { p ⁡ ( A , z ) if ⁢ ⁢ Az ∉ T m ⁢ ⁢ A ⁢ ⁢ and ⁢ ⁢ A ∉ T m ⁢ ⁢ A p ⁡ ( A , z ) × A · m if ⁢ ⁢ Az ∉ T m ⁢ ⁢ A ⁢ ⁢ and ⁢ ⁢ A ∈ T m ⁢ ⁢ A Az · w if ⁢ ⁢ Az ∈ T m ⁢ ⁢ A where the values A.m and Az.w are obtained from the .m and .w columns of the max-ARPA table T mA , respectively, and p(A,z) is computed from the .p and .b columns of the max-ARPA table.