Americans are spending more time watching television and surfing the Internet simultaneously, and nearly 60 percent of TV viewers use the Web at the same time at least once a month, according to a Nielsen report released on Monday. The Nielsen Three Screen Report said the findings in its study belied early concerns that the growing popularity of the Web would kill off traditional TV. The report for 2009’s fourth quarter, which tracked viewing across TV, the Internet and mobile phones, found a 35 percent rise in the amount of time Americans used the TV and Internet simultaneously compared with the same quarter in 2008. It found Americans now spend 3.5 hours per month watching TV while on the Internet. Active mobile video users grew by 57 percent over the year to 17.6 million from 11.2 million people, with much of the increase attributed to the growth of smartphones. The report found that Americans now watch about 35 hours of TV per week and two hours of time-shifted TV via video recorders (DVR), with 25 to 34-year-olds making more use of time-shifting than any other age group. DVRs are now found in 35 percent of American households, the report said.