Are you familiar with any of the research on the topic?

Past about 40 hours / week, across a wide range of jobs, it's more cost effective to hire new employees than to take the marginal reduction in performance.

> per-capita evolution

Like the early days of the Soviet Union, when the country went from being one of the most backward countries of Europe to having space travel? Is that your metric?

Regardless, you haven't presented data, only conjectured that such data exists.

> if you have a whole country doing more in a sustained way

Your "if" carries a lot of weight.

You need to show that such a country exists. Present data please.

Here's are more examples of how 80 hours/week is not realistic for an entire country's workforce.

"The Productivity of Working Hours", John Pencavel, The Economic Journal, Volume 125, Issue 589, 1 December 2015, Pages 2052–2076, https://doi.org/10.1111/ecoj.12166 and https://docs.iza.org/dp8129.pdf

] The estimates above on the output-hours relationship suggest that, for most [observed British munitions workers during WWI], weekly output rises with weekly hours of work although, after a point, the increase in output declines as more hours are worked. This point where the marginal product starts to decline varies with the workers and with the work done. For hours of 48 or less, weekly output tends to be proportional to weekly hours worked and the decline in the marginal product of hours occurs after 48 weekly hours.

See the Marginal Product of Hours in Table 5? After about 48 hours, it's better for the company to hire someone else. After about 65 hours per week, the marginal value is negative. See also Table 4 "Implied Output-Hours Relations Corresponding to Two Fitted Spline Functions".

Or from "The effects of working time on productivity and firm performance: a research synthesis paper", Lonnie Golden (2011) at http://www.ilo.org/wcmsp5/groups/public/---ed_protect/---pro...

] Shepard and Clifton (2000) established that manufacturing productivity does not necessarily improve when hours are lengthened. Their empirical study of aggregate panel data for 18 manufacturing industries within the US economy suggests that the use of overtime hours actually lowers average productivity, measured as output per worker hour, for almost all of the industries in the sample, even when the data are controlled or corrected. More precisely, a 10-per cent increase in overtime resulted, on average, in a 2.4-per cent decrease in productivity measured by hourly output.

] Indeed, it appears that in many, if not most, industries in the United States, shorter hours are actually associated with higher rates of output per hour (Holman et al., 2008, see Figure 1). ...

] A recent analysis of 18, mostly European, Member countries of the Organisation for Economic Co-operation and Development explores the degree to which longer annual hours have been associated with per-hour productivity at the national level, since 1950. It finds that the responsiveness of per-hour productivity for a given increase in working time is always negative. Not only are there decreasing returns on added working time, the returns in the form of added production diminish more rapidly for longer working times. When annual working time climbs above a threshold of 1,925 hours, a 1-per cent increase in working time would lead to a decrease in productivity of roughly 0.9 per cent at the threshold and a fully proportional decrease of 1 per cent past the threshold of 2,025 hours (Cette et al., 2011).

Or for South Korea, "When Less is More: The Impact of the Regulation on Standard Workweek on Labor Productivity in South Korea", WooRam Park, Yoonsoo Park (2019) https://doi.org/10.1002/pam.22136

] Taking advantage of the stepwise introduction of the standard 40-hour workweek in Korea, we apply a difference-in-differences framework to individual-level cross-sectional and plant-level longitudinal data to examine the impact of the policy on working hours and output, respectively. We find that the policy reduced per-worker hours but increased per-worker output, which is robust to various specifications and sample restrictions.

Or for Japan, "Why Do the Japanese Work Long Hours? Sociological Perspectives on Long Working Hours in Japan", Hiroshi Ono (2018) at https://www.jil.go.jp/english/jli/documents/2018/005-03.pdf :

] From the perspective of human resources, long workdays are a problem because: 1. Long workdays produce waste and inefficient allocation of human capital. Both at the firm and macro-economic levels, Japan is less productive than the OECD average. Return on equity (ROE), one indicator of corporate performance and profitability, is far lower than their counterparts’ in Europe and in the U.S. meaning that they are using capital less efficiently than their Western counterparts do.

] Figure 1 shows the relationship between working hours and productivity (expressed as GDP/ working hours) in OECD countries. The correlation between the two is -0.78, and
is statistically significant (p<0.001).

South Korea's productivity (GDP per working hour) is about like Poland, and the only country listed with longer working hours per annum than South Korea is Mexico.