For example, average yields of corn (maize) in the US have increased from around 2.5 tons per hectare (t/ha) (40 bushels per acre) in 1900 to about 9.4 t/ha (150 bushels per acre) in 2001.
fɔːɹ ɛɡzˈæmpəl, ˈævɹɪdʒ jˈiːldz ʌv kˈɔːɹn mˈeɪz ɪnðə jˌuːˈɛs hæv ɪŋkɹˈiːst fɹʌm ɚɹˈaʊnd tˈuː.fˈaɪv tˈʌnz pɜː hˈɛktɛɹ tˈiː slˈæʃ hˈɑː fˈoːɹɾi bˈʊʃəlz pɜːɹ ˈeɪkɚ ɪn nˈaɪntiːnhˈʌndɹɪd tʊ ɐbˌaʊt nˈaɪn.fˈoːɹ tˈiː slˈæʃ hˈɑː wˈʌnhˈʌndɹɪd fˈɪfti bˈʊʃəlz pɜːɹ ˈeɪkɚ ɪn tˈuː θˈaʊzənd wˈʌn.