9. The method of claim 1 , further comprising: pooling the plurality of utterances from the plurality of time periods, to yield pooled utterances; assigning each utterance of the pooled utterances to one of a plurality of subpopulations; generating a language model for each of the plurality of subpopulations; reassigning each utterance to one of the plurality of subpopulations according to a reassignment criterion; determining whether any of the plurality of subpopulations fulfill a splitting criterion; and splitting ones of the plurality of subpopulations that fulfill the splitting criterion, wherein: examining a subset of the plurality of utterances from each of the time periods, determining one of a significant word change within the plurality of spoken utterances, generating, from the subset of the plurality of utterances, a first cluster of utterances including a word corresponding to the significant word change, and generating, from the subset of the plurality of utterances, a second cluster of utterances not including the word corresponding to the significant word change are performed after pooling, assigning, generating a language model, reassigning, determining whether any of the subpopulations fulfill the splitting criterion, and splitting.
9. The method of claim 1 , further comprising: pooling the plurality of utterances from the plurality of time periods, to yield pooled utterances; assigning each utterance of the pooled utterances to one of a plurality of subpopulations; generating a language model for each of the plurality of subpopulations; reassigning each utterance to one of the plurality of subpopulations according to a reassignment criterion; determining whether any of the plurality of subpopulations fulfill a splitting criterion; and splitting ones of the plurality of subpopulations that fulfill the splitting criterion, wherein: examining a subset of the plurality of utterances from each of the time periods, determining one of a significant word change within the plurality of spoken utterances, generating, from the subset of the plurality of utterances, a first cluster of utterances including a word corresponding to the significant word change, and generating, from the subset of the plurality of utterances, a second cluster of utterances not including the word corresponding to the significant word change are performed after pooling, assigning, generating a language model, reassigning, determining whether any of the subpopulations fulfill the splitting criterion, and splitting. 13. The method of claim 9 , wherein the reassignment criterion comprises a subpopulation that maximizes a probability of an utterance occurring.