The world's fleets of cargo ships are aging, and demand for commodities is surging. That means the cost of shipping will go up, pushing up prices and crimping supply. The top performing ETF year to date is Market Vectors Steel SLX, which has returned 72.65%. Other ETFs with big gains were iShares Dow Jones (NYSE:DJ) U.S. Oil Equipment IEZ, iShares S&P Global Materials Sector Index Fund, MXI and WisdomTree Basic Materials DBN. The iShares ETFs returned 41.60% and WisdomTree Basic Materials returned 38.43% year to date. The price of oil was a big factor for the iShares ETF, and that price in part reflects the cost of transport, just as with many other commodities. Shipping costs are measured by the Baltic Exchange Dry Index, an indicator of prices for transporting freight.