To find articles with statistics, use the following keywords: percentage, percent, and statistics. To illustrate, if you want to find a newspaper article containing statistics on dog owners, search the LexisNexis Academic or Newspaper Source databases using the keywords: dog owners statistics. Further, try the specialty databases below.

Proquest Statistical - Provides access to a wide-range of statistics produced by governmental organizations. Great place to go for current statistics on almost any topic.
Statistical Abstract of the United States - A national book of statistics that reflect the social and economic condition of the United States.
U.S. Census Bureau - They're not just about population! Also a good source for data about agriculture, education, employment, health, law, etc.
Fedstats - Provides statistics produced by more than 100 US Federal Government agencies.
Data-Planet - Provides easy access to a wide variety of economic, social, and political indicators.