Even though online retailers reported strong "Cyber Monday" sales this week, another piece of data suggests shoppers are reining in their online spending.

The Online Publishers Association's Internet Activity Index report says that the share of time spent on commerce sites dropped to 12.8% in October. The share was 16.1% in January, representing a drop of more than 20%.

The other categories in the index include communications, community, content and search. Content, the largest category, grew to 45.3% from 42.7% in January.

The figures are based on data captured by Nielsen Online and provided to the OPA. The OPA did not disclose which sites were part of the index, but says Amazon, eBay, Shopping.com and Dell.com are examples of retailers included in the commerce segment.

Sources cited, referenced, or consulted: online-publishers.org, ClickZ, Wall Street Journal.