the black economy
noun🔊/ðə ˌblæk ɪˈkɒnəmi/
🔊/ðə ˌblæk ɪˈkɑːnəmi/
(British English) (North American English the underground economy)
[singular]business activity or work that is done without the knowledge of the government or other officials so that people avoid paying tax on the money they earn 黑市经济；黑市经营；地下经济活动