GTAPM - GTAP model with marketing margins

There are marketing margins on all intermediate inputs purchases
by firms (both domestic and imported), commodities purchased by
the private household and the government household, and on commodities
going for export (margins to get the good to the border).

The model has 3 regions:  USA, EU, and ROW.

Currently, we only have data on US margins from the 1992 IO table.

Have applied those margins to the EU and ROW.

The model includes 7 commodities:  5 commodities to closely match the aggregation of
Frisvold plus 2 margin commodities.

crops = pdr, wht, gro, osd, c_b, pfb, v_f, ocr
live = ctl, oap, rmk, wol
food = fish, cmt, omt, vol, mil, pcr, b_t, sgr, ofd
mnfcs = for, col, oil, gas, omn, ppp, crp nfm, mvh, otn, ele, tex, wap, lea,
        lum, p_c, nmm, i_s, fmp, ome, omf
svces = ely, gdt, wtr, cns, cmn, ofi, isr, obs, ros, osg, dwe
trd = trade:  trd
trans = transportation:  otp, wtp, atp


