http://www.arbitron.com/ has been crawled 543 times going all the way back to December 19, 1996.

A crawl can be a duplicate of the last one. It happens about 25% of the time across 420,000,000 websites. FAQ
Jan

January 1, 2011

1 snapshot

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January 8, 2011

2 snapshots

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January 10, 2011

1 snapshot

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January 12, 2011

2 snapshots

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January 13, 2011

1 snapshot

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January 22, 2011

1 snapshot

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January 24, 2011

1 snapshot

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January 25, 2011

1 snapshot

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Feb

February 1, 2011

1 snapshot

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February 2, 2011

1 snapshot

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February 6, 2011

1 snapshot

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February 8, 2011

2 snapshots

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February 9, 2011

1 snapshot

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February 10, 2011

1 snapshot

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February 12, 2011

2 snapshots

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February 19, 2011

1 snapshot

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Mar

March 1, 2011

1 snapshot

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March 5, 2011

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March 14, 2011

1 snapshot

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March 25, 2011

1 snapshot

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Apr
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April 11, 2011

1 snapshot

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April 14, 2011

1 snapshot

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April 21, 2011

2 snapshots

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May
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May 9, 2011

1 snapshot

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May 17, 2011

1 snapshot

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May 18, 2011

1 snapshot

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May 31, 2011

1 snapshot

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Jun
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June 6, 2011

1 snapshot

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June 8, 2011

1 snapshot

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June 18, 2011

1 snapshot

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June 28, 2011

1 snapshot

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Jul
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July 7, 2011

1 snapshot

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July 9, 2011

1 snapshot

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July 10, 2011

1 snapshot

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Aug
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Sep
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Oct
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Nov
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Dec
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Note

This calendar view maps the number of times http://www.arbitron.com/ was crawled by the Wayback Machine, not how many times the site was actually updated. More info in the FAQ.