9. An article of manufacture comprising at least one non-transitory computer readable medium containing one or more programs which, when executed by at least one processor, cause the at least one processor to perform a method comprising: obtaining first data from a plurality of calls routed by a natural language call routing system that uses a first speech recognition model to recognize speech of the plurality of calls and a first action classification model to route calls based on the recognized speech, first data comprising audio data from the plurality of calls, a first N-best list of word sequences generated by using the first speech recognition model to recognize at least a portion of the audio data and associated call classification data indicating how each of the plurality of calls were routed by the natural language call routing system; and modifying the first speech recognition model and the first action classification model based at least in part on the first data, including using the first N-best list of word sequences, to obtain a second speech recognition model and a second action classification model; and modifying the second speech recognition model and the second action classification model based at least in part on the first data to obtain a third speech recognition model and a third action classification model, wherein the modifying comprises modifying the second speech recognition model and the second action classification model by using the first N-best list or a second N-best list of word sequences generated by using the second speech recognition model to recognize at least the portion of the audio data.
9. An article of manufacture comprising at least one non-transitory computer readable medium containing one or more programs which, when executed by at least one processor, cause the at least one processor to perform a method comprising: obtaining first data from a plurality of calls routed by a natural language call routing system that uses a first speech recognition model to recognize speech of the plurality of calls and a first action classification model to route calls based on the recognized speech, first data comprising audio data from the plurality of calls, a first N-best list of word sequences generated by using the first speech recognition model to recognize at least a portion of the audio data and associated call classification data indicating how each of the plurality of calls were routed by the natural language call routing system; and modifying the first speech recognition model and the first action classification model based at least in part on the first data, including using the first N-best list of word sequences, to obtain a second speech recognition model and a second action classification model; and modifying the second speech recognition model and the second action classification model based at least in part on the first data to obtain a third speech recognition model and a third action classification model, wherein the modifying comprises modifying the second speech recognition model and the second action classification model by using the first N-best list or a second N-best list of word sequences generated by using the second speech recognition model to recognize at least the portion of the audio data. 12. The article of manufacture of claim 9 , wherein the first data further comprises call transfer pattern data.