2009 suggests that these measures have experienced a dramatic growth in recent years due to three concurring factors:

* improvements in the level of literacy (including statistical)
* increased complexity of modern societies and economies, and
* widespread availability of information technology.

According to Earl Babbie, items in indices are usually weighted equally, unless there are some reasons against it (for example, if two items reflect essentially the same aspect of a variable, they could have a weight of

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