NYSE Arca and the Chicago Board Options Exchange have decided to close trading for options on exchange-traded funds 15 minutes earlier to synchronize the timing with the close of trading of the underlying assets. Arca last month decided to move up the closing time for ETFs to 4 p.m. Eastern time, to better accommodate after-hours trading and coordinate daily value reporting with fund managers’ daily asset value calculations. Arca is one of the largest marketplaces for ETFs, attracting 128 listings in 2008 alone. CBOE is following in Arca’s footsteps because it trades a large variety of ETF options, and wanted to synchronize its trading with the prevailing marketplace. About 50 options classes are affected.