hda Herfindahl
He do luOng da clang h6a mat hang xuat khau, nhieu nghien ciru da truc tier, sir dung cac chi tieu do luting mirc do tap trung hoa mat hang xuat khau Herfindahl. Day la nhang chi s6 do lueng khai niem tap trung h6a xuat khau — mot khai niem di lap voi mirc dO da clang hoa mat hang xuat khau. Neu nhu re) hang xuat khau cua mot qu6c gia c6 cac chi s6 tap trung h6a xuat khau cao, dieu do chung to qu6c gia dO c6 mire dO da clang h6a mat hang xuat khau thdp va ngugc lai. Theo Petersson (2005) va Matthee va Naude (2007), Salomon Samen (2010) chi s6 nay dugc tinh nhu sau:
n r, \ 2
(1.9)
Trong do: HI la mirc dO tap trung cita gio hang Ma xuat khau xi la gia tri xuat khau dm mat hang i
X la tong gia tri xuat khdu cita qu6c gia n la s6 san pham xuat khdu cua que)c gia.
Chi so HI nhan gia gi tir 0 den 1. Gia tri HI cang 16n thi xuAt khau cita qu6c gia do cang tap trung nhieu vao mot s6 mat hang nhat dinh. Ngugc lai, HI cang nhO thi mirc d6 da clang h6a xuAt khAu cang cao. Tfic la xuat khAu dugc phan b6 ra nhieu loci hang hoa khac nhau. Chandra, Vandana, Jessica Boccardo va Israel Osorio-Rodarte (2007) da phan chia cac gia tri dm chi s6 HI 6 danh gia su da dang hoa mat hang xuAt khAu, cu the la: Neu HI<0,05 thi qu6c gia dO co mix d6 da clang hoa xuAt khau rat cao; tir 0,05 < HI < 0,1 da clang h6a xuAt khau mix d6 Wong d6i ca.(); tir 0,1< HI < 0,2 da dang hoa a mirc d6 trung binh; Tir 0,2< HI < 0,4 co. cAu xuAt khAu mirc d6 tucmg d6i tap trung; HI > 0,4 thi co. cAu xuAt khAu cua qu6c gia dO co mix d6 tap trung rat cao.
M6t s6 ngugi khong sir dung tivc tiep chi s6 mirc d6 tap trung h6a Herfindhal, thay vi do h9 xay Ong cac chi s6 do luting da Ong h6a mat hang xuAt khAu. Manuel R. Agosin (2007) da de xuAt chi s6 cach tfnh chi s6 da clang h6a mat hang xuat khau nhu sau:
ED= 1 -HI (1.10)
COn Manuel Heredia Caldeira Cabral va Paula Veiga (2010) lai tinh town chi s6 da clang h6a mat hang xuat khAu bang each lAy nghich dao chi s6 Herfindhal. Khi do chi s6 da clang hoa mat hang xuat khau dugc xac dinh nhu sau:
ED = 1/HI (1.11)
Trong do: ED la mirc d6 da clang hOa cita gi6 hang h6a xuAt khAu HI la chi s6 Herfindhal
Chi s6 ED cang cao chi ng to cac mat hang xuat khAu cua qu6c gia cang da clang hoa va ngugc lai.
