Choice of measure for unemployment There are six types of unemployment rates in the US (U1-U6). U6 provides the broadest measure of unemployment, taking into account not only the unemployed labour market participants who are actively seeking for jobs, but also the marginally affected, the discouraged, as well as the part-time workers who would like to have a full-time job (i.e. "underemployed" workers). This broad measure is deemed by numerous economists to be the "true" unemployment rate. However, what is usually popularised in the news media is in fact, the U3 unemployment rate, which only takes into account those unemployed that are actively seeking for jobs. What is the reason for the U3 rate being the more popularised and widely emphasised measure of unemployment in the United States and also for other developed economies?
What is the reason for the U3 rate being the more popularised and widely emphasised measure of unemployment in the United States and also for other developed economies? 


Historically, data for U-3 have been collected for longer than U-6.

For example, in the US, the former have been collected since 1948, while the latter only since 1994. So, it is "traditional" to report the U-3 data.

In many other countries, the equivalent of U-6 data may not even be collected.

So, when making comparisons across time and countries, U-3 data are the best we've got. 


  This broad measure is deemed by numerous economists to be the "true" unemployment rate.


This is incorrect. Economists do not consider any single measure to be the "true" unemployment rate. Instead, to arrive at any conclusion, economists try to look at a broad variety of measures and data, where available.

(But again, for reasons already given above about data availability, economists will often use only the U-3 data. This though should not be misconstrued as them thinking that this is the "true" unemployment rate. In fact, the deficiencies of the U-3 data is exactly why economists encourage collecting also other measures of unemployment.)