Pelaku underground economy lebih menyukai penggunaan uang kartal dalam transaksinya karena lebih sukar dilacak oleh aparat negara dibanding jenis uang yang lain. Jika aktivitas underground economy meningkat, maka permintaan terhadap uang kartal pun semakin meningkat. Penelitian ini mencoba mengukur besarnya underground economy di Indonesia melalui analisis sensitivitas permintaan uang kartal terhadap adanya beban pajak. Besarnya underground economy di Indonesia periode 2000 ? 2009 sekitar 5,03% - 5,04% dari PDB. Potensi pajak atas aktivitas ekonomi tersebut mencapai sekitar Rp 18,76 Triliun - Rp 18,77 Triliun setiap tahunnya.

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Economics agents in the underground economy prefer cash payments in their transaction because it is not easy to be tracked by the state apparatus than other types of money. If the underground economy activity increases, the demand for money (currency) also increasing. This study attempts to measure the underground economy in Indonesia use the currency demand method. The size of the underground economy in Indonesia during the period 2000 - 2009 is around 5.03 - 5.04 as a percentage of GDP. Meanwhile, the tax potential on the activity is around Rp 18.76 trillion - to Rp 18.77 trillion annually.