16.7 Minimum cost trading to achieve target sector exposures. A current portfolio is given by the n-vector heur, with the entries giving the dollar value invested in the n assets. The total value (or net asset value) of the portfolio is 1 heurr. We seek a new portfolio, given by the n-vector h, with the same total value as hcurr . The difference h-hcurr is called the trade vector; it gives the amount of each asset (in dollars) that we buy or sell. The n assets are divided into m industry sectors, such as pharmaceuticals or consumer 16.7 Minimum cost trading to achieve target sector exposures. A current portfolio is given by the n-vector heur, with the entries giving the dollar value invested in the n assets. The total value (or net asset value) of the portfolio is 1 heurr. We seek a new portfolio, given by the n-vector h, with the same total value as hcurr . The difference h-hcurr is called the trade vector; it gives the amount of each asset (in dollars) that we buy or sell. The n assets are divided into m industry sectors, such as pharmaceuticals or consumer