Media and entertainment, financial services, travel, and automotive are expected to account for more than half of the total spending on online advertising in five years, a market researcher says.

The four industries will spend $11.5 billion in 2011, comprising 57% of all online ad spending that year, according to JupiterResearch. Spending is expected to increase across all industries, but the four biggest spenders are likely to open their wallets wider to take advantage of consumer trends.

Many people use the Web to search for the best prices for plane tickets, hotels, car rentals, and other travel-related services. In addition, a growing number of online consumers use the Web for online banking and to research automobiles, watch videos, and listen to music.

In five years, automotive and travel advertisers will be the third and fourth largest spenders, respectively, JupiterResearch said. Media and entertainment will be the largest online ad category, accounting for more than a quarter of search advertising alone. Financial services will be the second biggest ad spender.

With consumers spending as much time online as watching TV—a median of 14 hours a week—the shift of budgets to online advertising is inevitable, JupiterResearch said.