Hermanto Siregar IPB University   Jl. Raya Darmaga Kampus IPB, Babakan, Kec. Dramaga Bogor, Jawa Barat 16680 Indonesia   hsiregar@apps.ipb.ac.id   www.ipb.ac.id           JEL Areas: O4 : Economic Growth and Aggregate Productivity: General R1 : General Regional Economics (includes Regional Data)