8. A system comprising: a processor; a transceiver; data storage; and program instructions in the data storage that, upon execution the processor, cause the system to train an automatic speech recognition (ASR) system with sample utterance-to-text-string mappings, wherein the sample utterance-to-text-string mappings are selected from a corpus of utterance-to-text-string mappings based on a first compressed word frequency and a second compressed word frequency, wherein the first compressed word frequency was determined by raising a first uncompressed word frequency to a power, wherein the power is greater than or equal to 0 and less than 1, wherein the second compressed word frequency was determined by raising a second uncompressed word frequency to the power, and wherein at least one of the first compressed word frequency and the first uncompressed word frequency was received by the system via the transceiver.
8. A system comprising: a processor; a transceiver; data storage; and program instructions in the data storage that, upon execution the processor, cause the system to train an automatic speech recognition (ASR) system with sample utterance-to-text-string mappings, wherein the sample utterance-to-text-string mappings are selected from a corpus of utterance-to-text-string mappings based on a first compressed word frequency and a second compressed word frequency, wherein the first compressed word frequency was determined by raising a first uncompressed word frequency to a power, wherein the power is greater than or equal to 0 and less than 1, wherein the second compressed word frequency was determined by raising a second uncompressed word frequency to the power, and wherein at least one of the first compressed word frequency and the first uncompressed word frequency was received by the system via the transceiver. 12. The system of claim 8 , wherein the sample utterance-to-text-string mappings were selected by the system, and wherein selecting the sample utterance-to-text-string mappings comprises: determining a first word selection probability for a first word based on the first compressed word frequency divided by a first word frequency of the first word, wherein the sample utterance-to-text-string mappings include a particular utterance mapped to a particular text string, and wherein the particular text string contains the first word; and selecting the particular utterance based on the first word selection probability.