Ben Muse informs that the most recent National Economic Trends of the St. Louis Fed has a short cover story by Michael Pakko on trends in labor's share of U.S. national income.

His figure shows his estimate of total labor compensation by year since 1948 (including wages, salaries, employer social insurance contributions and benefits, an estimate of the labor portion of proprietors' income) and and an estimate of wage and salary income:

"...The dashed line shows wage and salary income as a fraction of national income. This measure clearly shows a declining trend in recent decades. Having reached a peak of 58 percent in 1970, wages and salaries have declined to only 52 percent of national income in 2003. However, if we consider total compensation—including employer social insurance contributions and benefits—labor’s share has shown very little variation. By this measure, labor’s share of national income has averaged 70.5 percent over the past 50 years and has remained within a narrow range of that average..."

This is one of Kaldor's stylized facts:

The concept of GNP was only developed in the early twentieth century, not for measuring economic growth, but for assessing the state of a national economy. Not long after, Kaldor (1961) observed that the ongoing growth in per capita national income came with several empirical regularities:

• Income per capita grows steadily over long stretches of time;
• Factor income shares--the fractions of total income accruing to the labor force and to physical capital--show no secular trend;
• The ratio of total national income to the aggregate stock of physical capital--the total value of machines, highways, bridges, buildings, physical infrastructure--remains roughly constant.

These observations, typically labeled Kaldor's stylized facts, constitute a first important growth measurement that economists sought to understand and to explain. According to Kaldor's measurements, while economic growth occurs, its benefits divide up in a stable way between rewards to capital and labor--no one factor input, taken as an aggregate, benefited more than another from economic growth. Moreover, since capital's income share can be viewed as the stock of capital multiplied by capital's rate of profit, Kaldor's stylized facts also implied that the profit rate is, in the long run, constant. {by Danny Quah, Source}

Those facts were presented by the British economist Nicholas Kaldor on a 1958 conference on capital accumulation (most economics textbooks also attribute the observation that the growth rate of output per worker differs substantially across countries to Kaldor).

Here are some new stylized facts[1]:

1. Factor accumulation does not account for the bulk of cross-[country] differences in the level or growth rate of GDP per capital; something else – total factor productivity* – accounts for a substantial amount of cross-country differences.
2. Divergence: There are huge, growing differences in GDP per capita. Divergence – not conditional convergence – is the big story.
3. Growth is not persistent over time. Some countries “take off,” others are subject to peaks and valleys, a few grow steadily, and others have never grown. In contrast, capital accumulation is much more persistent than overall growth.
4. All factors of production flow to the same places, suggesting important externalities.
5. National policies influence long-run growth.

Seems there is still some work to be done...


* Here is a non-mathematical introduction to growth accounting (by Brad Delong).

[1] It's Not Factor Accumulation: Stylized Facts and Growth Models,
March 2001, William Easterly & Ross Levine