2 Gross imports reported as "ore content."

Bureau of Mines not at liberty to publish figures.

NOTE.-General imports in 1929; imports for consumption in 1935 and 1937.

steel suitable for machine tools. These and others are essential in the production of war materials. Yet even for most of these strategic minerals the country is less dependent on foreign resources than the imports would indicate. In the case of the minerals italicized in the table there are deposits which could be worked if foreign supplies were cut off or became too expensive. Only in the case of the 8 items not italicized, of which the most important are nickel, tin and manganese, is the country dependent on foreign sources. A two year's war supply of these items, if they could be obtained at 1935 prices, would cost only approximately 114 million dollars, while a year's peace time requirement in 1937, measured by the imports of that year, was purchased for 163 million dollars. This essential independence of foreign resources means that the natural resources which primarily affect the structure of the American economy are the resources of the continental United States.

Productive Plant

Of secondary importance for longer periods, but of great importance for shorter periods, is the productive plant which men have developed. In the course of the centuries during which the continent has been inhabited, productive instruments for making use of natural resources have been developed and now exist in the form of the buildings, equipment, and improvements. This productive plant includes that employed in all the branches of economic activity, in agriculture, mining, manufacturing, trade, construction, government, the service industries, and residential housing.

The total value of this plant in 1935 was something like 190 billion dollars divided among major categories in the manner indicated in chart I. These figures represent the very crudest sort of estimates. In making the estimates, farm buildings and equipment have been included as agricultural plant, but land has been excluded on the ground of its being primarily a natural resource. Some part of the value of agricultural land is the result of man-made improvements such as drainage and irrigation but no data were available to make such an allocation. The structural significance of the specific categories will become apparent in the discussion of the structure of production in chapter V.

The structural significance of the productive plant as a resource is primarily a short-run matter of location and of industrial mobility. Manmade plant differs from natural resources in not being fixed and located by nature. A new plant can be built; a new mineral deposit can only be found. Plant location thus does not constitute the same fixed element in the structure

of the economy as does the location of natural resources. At the same time, existing plant, until it becomes obsolete or wears out, is like a fixed natural resource except to the extent that it can be dismantled and in part removed to a new location as some textile mills were moved from New England to the South. Thus, the national plant can be thought of as capable of a gradual change in location as particular buildings and equipment wear out or become obsolete and are replaced by new buildings and equipment in new locations, and as equipment is occasionally transferred from one region to another.

Existing plant represents an element of relative fixity in relation to type of industrial activity as well as of place. Many buildings and even some equipment may be put to various uses. But insofar as buildings and equipment are specialized, like a railway locomotive or a knitting frame, they give direction to activity until they are abandoned or replaced by plant designed for other uses.

The possible speed of this slow mobility of plant is suggested by the rate at which new plant and equipment is built. In the period since 1919 new plant was built at a rate to duplicate the value of the total existing plant in approximately 15 years. A rough indication of the mobility of the major categories of plant are given in table III below:

1 Industrial includes manufacturing, mining, utility, trade, and construction and services other than government and residential housing.

The secondary importance of the existing plant can be seen by comparing its value with the annual production of the country. In 1929 and again in 1937 the national production amounted to approximately 66 billions of 1935 dollars. Since the productive plant amounted in 1935 to approximately 190 billion dollars the plant is only equal to the value of approximately three years of production at the levels of those years. If residential housing and government plant be excepted the value of the total agricultural and industrial plant would be equal to less than 2 years' production at that

It must not be assumed that plant mobility depends only on the replacement rate. The presence of a skilled labor supply, ancillary industries, and established business relations tend to hold an industry in its old location even when new plants are being constructed.

level. If the whole waste of the depression due to idle men and idle machines could have been used to build agricultural and industrial plant, the existing plant could have been completely rebuilt. Thus, in comparison with annual production or with the wastes of depression, existing plant is not of dominant longrun importance. It is mainly important for the structure of the economy as its character and location condition the structure of production in the immediate future.

Manpower

Manpower is by far the most important resource of the Nation and the resource likely to involve the largest waste. The millions of individual workers constitute the backbone of production, and their activity as skilled and unskilled workers, managers, artisans, farmers, teachers, doctors, or independent business men, provides the primary basis for the nation's standard of living. Correspondingly, if available workers are idle, production and level of living are lower than resources make possible. Manpower, potential work, is a perishable resource like water-power. Ten or fifteen million idle workers combined with idle machines can mean a tremendous loss in potential national income. In addition, the failure to use available manpower reduces the effectiveness of future production as idleness breeds frustration and loss of skills. The magnitude of losses from waste of manpower throw the wastes in the exploitation of natural resources into insignificance.

Just what constitutes the nation's available manpower is a question which cannot be easily answered. Much of the productive activity of the country is carried on within the homes as the housewife prepares meals, keeps house, nurses children, launders clothes, and carries on the numerous home activities. Yet the available statistics are geared to throw light only on, manpower available for gainful activity, i. e., activity aimed to bring in money income. From the point of view of the structure of the whole economy this part of the total manpower is undoubtedly the more significant in that the organizational structure concerns primarily the relations among these gainfully employed. An approximate idea of the manpower available for gainful employment can be obtained from the census of occupations. As of April 1, 1930, the date of the most recent occupational census, 48,829,920 persons, or v 39.8 percent of the population reported themselves as "gainfully occupied." This figure includes not only wage and salaried workers but business and professional workers, farmers and unpaid family workers on farms. It includes people who were temporarily unemployed but does not include persons who were seeking employment but had not yet held a job. It probably includes

Source: Based on Fifteenth Census of the United States: 1930, Population, volume V, page 115.

some persons who had retired but might be induced to take gainful employment if conditions made such employment desirable. Very probably it includes many persons who were unwilling to report that they had no gainful occupation. The figures for gainfully occupied taken from the occupational census can only give an indication of the magnitude of the available manpower and its characteristics and should not be regarded as precise.

An indication of the age and sex distribution of the gainfully occupied in 1930 is given in chart II. Approximately a quarter of the gainfully occupied were women and three-quarters were men. When the gainful workers are grouped by five-year age intervals the largest number of gainful workers fall in the 20-24 year age group; the bulk of workers fall between the ages of 20 and 55, 77 percent of the men and 76 percent of the women falling into this range.

The proportion of each age group reporting themselves as gainfully occupied throws further light on the characteristics of the available manpower. The percentages for men and women are indicated separately in chart III. For the men, the highest proportion gainfully occupied in any age group is in the group between

35 and 39, 98 percent of this group being occupied. For the women, the highest proportion occupied is in the 20-24 year group, 42 percent being gainfully occupied. Over 95 percent of the men between 20 and 55 reported themselves as gainfully occupied but only 27 percent of the women.

The figures given above may suggest that with any given population the available manpower is a fixed amount. Actually, the number of workers available is not fixed, but varies with conditions. For example, there is a clear relationship between the supply of labor and the level of real earnings. The higher the level of earnings, the smaller the proportion of the population which will seek work. This does not mean that higher wage rates in a community will not draw in more workers. Rather it reflects the fact that as the principal earner of a family gets higher earnings, either because of fuller employment or higher wage rates, there is less need for other members of the family to work. Children can be kept in school longer, the old folks can retire earlier, and the housewife can remain at home.

2

The influence of the level of earnings on the labor supply is appraised in a recently published analysis of the statistics of the gainfully occupied in cities with different levels of earnings. The results of this analysis are summarized in chart IV which shows the correlation between average earnings in 37 cities and the number of persons over 10 years of age per thousand of population reporting themselves as gainfully occupied.3 The line on the chart indicates the approximate relation between earnings and the proportion of the population seeking work. It suggests that if the earnings of adult male workers averaged $2,000 a year, and women's wages bore the customary relation to men's, roughly 44 percent of the urban population would be in the gainfully occupied class; whereas if the average earnings of adult male workers were $1,000 a year, women's earnings corresponding, over 48 percent of the population would be employed or seeking employment. There is thus evidence of some variation in the total manpower available as earnings themselves vary.

2 "Studies in the Supply Curve of Labor; the Relation in 1929 between Average Earnings in American Cities and the Proportions Seeking Employment," by Erika H. Schoenburg and Paul H. Douglas, Journal of Political Economy, Vol. XIV, No. 1, February 1937.

Adjusted for differences in age distribution in different cities, age distribution in Chicago being used as the base. This is sufficiently typical of the urban population of the country to make the statement above generally applicable. It is to be noted that a larger proportion of the urban population tends to be employed than the 39.8 percent for the country as a whole. This is undoubtedly due in large part to the drawing of persons from the country to the city as they come of working age so that rural areas have more nonworking children per unit of population than do urban areas.

Four cities out of the 41 cities used in the study are excluded from the chart because o evidences of abnormality-Washington, D. C.; Scranton, Pa.; Salt Lake City, Utab and Fall River, Mass.