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the workplace. The chart above displays the
trend for each of these fi ve types of tasks.
Each trend refl ects changes in the numbers
of people employed in occupations emphasizing
that task. To facilitate comparisons, the
importance of each task in the U.S. economy
is set to zero in 1969, our baseline year. The
value in each subsequent year represents the
percentage change in the importance of each
type of task in the economy.
A quick look at the chart shows that, consistent
with our expectations, tasks requiring
pattern recognition grew in frequency while
rules-based tasks declined. Complex communication
is important in management and
in teaching and sales, among other occupations.
As the work structure evolved toward
these particular occupations, the frequency
of tasks requiring complex communication
grew steadily. The frequency of tasks requiring
expert thinking – tasks that
involved solving new problems –
followed a similar growth path.
For rules-based tasks where
computers can substitute for
humans, the picture is one of
decline. The share of the labor
force employed in occupations
that emphasized routine cognitive
tasks remained quite steady during
the 1970s and then declined
quite precipitously over the next
two decades.
The pattern for routine manual
tasks that might be subsumed
by automation is roughly similar:
a slight rise during the 1970s and
a steady decline thereafter. The
share of the labor force working
in occupations that emphasize non-routine
manual tasks declined throughout the period.
In part, this refl ects the movement of manufacturing
jobs offshore.
The data in the chart on page 69 (occupations)
and this page (tasks) are consistent
with our description of computers’ economic
impacts. But correlation does not prove
causation – the trend in both charts could
have been caused by other factors. To make
a stronger case, we must increase the level of
detail to look at changes within industries. If
the adoption of computers shifts work away
from routine tasks and toward tasks requiring
expert thinking and complex communication
it should be easier to identify within
expert thinking complex communication routine manual
routine cognitive non-routine manual
14
12
10
8
6
4
2
0
-2
-4
-6
-8
1969 1974 1979 1984 1989 1994 1999
PERCENT CHANGE IN EMPLOYMENT
ECONOMY-WIDE MEASURES OF ROUTINE AND
NONROUTINE TASK INPUT: 1969 - 1998
source: Revised version of fi gure from David Autor, Frank Levy and Richard J. Murnane, “The
Skill Content of Recent Technological Change: An Empirical Exploration,” Quarterly Journal of
Economics 118 (November 2003): 4.
Fourth Quarter 2004 75
industries. Specifi cally, we can ask: are those
industries that invested most heavily in computers
the industries where we see the greatest
changes in task structure?
The answer is yes. In the chart above, the
left of each pair of bars describes the average
change in task frequency within industries
between 1980 and 1998. The height
of the right bar in each pair is an estimate
of the change in task frequency that would
have occurred had there been no increase
in computer use. A comparison of the bars
in each pair shows that changes in task frequency
have been concentrated in the industries
experiencing the most rapid increases in
computer use.
This pattern is particularly striking for
routine cognitive tasks. The percentage of
the labor force employed in jobs that consisted
primarily of carrying out routine cognitive
tasks declined substantially over these
years. The chart shows that, in the absence of
changes in computer use, the estimated percentage
of the labor force working at routine
cognitive tasks would have increased. The
amount of routine information-processing
taking place in the economy grew substantially
over these years, but increasingly this
work was carried out by computers instead
of people.
The case for the link between computerization
and task change is strengthened by looking
at the changes in tasks performed by high
school graduates. Since 1970, industries that
invested heavily in computers shifted their
workforces away from high school graduates
and toward college graduates. This comes as
no surprise. On average, college graduates are
better suited than high school graduates for
jobs like product design, technical troubleshooting
　
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