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Table 4.—Number of sheep reported shorn by Utah farmers
DIFFERENCES BETWEEN NUMBERS REPORTED SHORN CURRENTLY (JULY) AND HISTORICALLY (FOLLOWINO JANUARY)
Current reports used as base. Number shorn not asked in July, 1924. hence only two years' data.
These are merely a few illustrations of memory bias among farmers. The farmer is asked to recall certain acreages and numbers of livestock which were on his farm a year earlier. Undoubtedly the extent of memory bias for a shorter period would be less than for a period of one year, but nevertheless may be considerable. The Bureau of Agricultural Economics once attempted to secure quarterly reports from operators of interior mills and elevators, requesting reports on stocks at the opening and close of the quarter, receipts and shipments during the quarter. Examination of a considerable number of schedules indicated that even the elevator operators, who presumably keep some sort of record of quantities of grain in store at all times, submitted reports relating to the same date which were not consistent.
The general conclusions which have been drawn and which are used constantly by the Bureau of Agricultural Economics in interpreting the reports of crop correspondents may be stated as follows:
1. When there has been but little actual change from one date to the next there is ordinarily relatively little memory bias in reports on most items, such as horses, cows, acreage of corn, wheat, etc. While there are many individuals who do not report the correct figures for the preceding date, the number who report too many is largely offset by the number who report too few. Ordinarily the memory bias on wheat, hay, horses, or cows is less than 1 per cent.
2. When a considerable period of time has elapsed the errors of those remembering too many is much less exactly offset by the errors of those remembering too few. Thus, during 1927 the number of cows in New York State increased slightly, and instead of the usual memory bias of remembering one-half of 1 per cent, too many reporters remembered 1.8 per cent too many. During the same year the number of horses declined and, in reporting for the previous year, crop correspondents remembered 2.1 per cent too few.
3. Memory bias is much greater in items of minor importance, or which change materially from month to month. For example, in reporting poultry on hand a year previous, crop correspondents apparently remember too few by 6 or 8 per cent. In the case of catch crops or others which are grown only occasionally, the memory bias is often quite heavy.
4. Memory bias is much heavier in the case of items for which there is no exact definition. For example, the momory bias on all corn as a whole is probably between 1 and 2 per cent in New York, but the memory bias on corn harvested for green feed or fodder only may exceed 20 per cent. The bias on oats is usually about one-half of 1 per cent, but the memory bias on grains cut green for hay is probably around 15 per cent.
5. On certain items there are certain twists of memory which are so frequently encountered that little reliance can be placed on the memory of crop reporters. Among these are such items as dairy heifers and other young stock, including colts, lambs, and pigs.
One of the most important results of statistical analysis of samples in the Bureau of Agricultural Economics has been the repeated proof of the necessity of comparability as between inquiries. The results of various inquiries have been endangered so often by even slight changes in wording, by changes in time of inquiry, or by changes in the type of farmer to whom the inquiry is sent that in the present conduct of the work comparability is stressed above everything else. It has been noted and statistically proven that, unless the general type of farmers replying to an inquiry on one date has practically the same composite as those replying on another date, the returns are likely not to be comparable, and the results of the analysis uncertain. For example, if on one date an inquiry is sent to a large number of general farmers and on another date is sent to a list of farmers among whom grain growers predominate, practically all ratios computed from the samples of the two dates would show so material a lack of comparability as to be practically useless as a basis for estimates. In like manner, if the wording of a particular inquiry is changed ever so slightly from one date to the next, some very astonishing results sometimes occur. The question of comparability of inquiries is so important that at times doubtful indications result from such a minor change as a misplacement of a comma in the inquiry. The time of the year and even the date of the month when an inquiry is made have a bearing upon the significance of the results. For example, the bureau, in making its forecasts of production based upon condition as of the 1st of the month, must maintain a well-defined schedule of dates upon which schedules shall leave Washington in order that none of the schedules shall reach the farmer too soon and that none shall reach him too late. In the event that there is a delay of even a few days in mailing out schedules, a distinct effect upon the resulting information has been noted.
In short, our experience emphasizes the conclusion that better results would be obtained if the information were obtained at about the same time of the year for each census period.
V. COMPLETENESS OF HARVEST BY JANUARY 1
While it is clear that there is a great advantage in having the enumeration taken at a time as nearly as possible to the completion of the harvesting of the crops, the question has been raised whether or not an earlier date, such as December 1 or January 1, would not be open to objection on the ground that so large a part of the harvest is yet incomplete that the farmer would not be able to give the information asked for. Apparently, however, this difficulty is not a serious one. As shown by the accompanying table, all the important crops are completely harvested by December 1, with the exception of the following:
Corn (husking), cotton (picking), tobacco (stripping), citrus fruits, peanuts (threshing), rice. It is desirable to consider each of these briefly.
Table 5.—Percentage of crops of United States harvested monthly
Table 5.—Percentage of crops of United States harvested monthly—Continued
Cotton.—Data obtained by the Bureau of Agricultural Economics indicate that, on the average, about 79 per cent of the crop of cotton is harvested by November 1, and all but less than 5 per cent by December 1. Only about 4 per cent is harvested after January 1 of the following year. The accompanying table shows the contrasts between a number of the States in this regard. It appears that Missouri and California are the only States where a large percentage of the cotton is harvested in December or January. Of course, these are averages for a period of years. In the individual years the amount harvested after December 1 may be smaller or larger than the average shown. However, the fact that the Bureau of the Census makes an annual enumeration of ginnings makes the regular census figures on production of cotton comparatively unimportant. The figures on production as determined by the regular census are not available for many months after the enumeration is made, whereas the ginning reports are available immediately.
Tobacco.—-While all the tobacco is not stripped by November 30, it is all cut and stored, and in many areas is stripped or marketed or ready for market, and every farmer has definite information as to the number of pounds he has produced. In fact, our figures show that, on the average, the entire crop of tobacco has been harvested by November 1.
Peanuts.—-Peanuts are gathered and largely marketed before the end of November, although in the northern areas a part of them may be still in the stack drying. Ordinarily, even then a large proportion of the nuts have been picked off, so that the yield is fairly well known. Our figures show that, on .the average, only three-tenths of the peanut crop remains unharvested on December 1.
Table 6.— Usual per cent of cotton harvested monthly
Rice.—A small quantity of late rice may be still unharvested on December 1. In fact, our figures show that on the average 2.4 per cent of the crop is harvested after December 1. However, this figure is so small that any margin of error in the farmer's estimate would have slight, if any, effect upon the reported size of the total crop.
Citrus fruits.—Citrus fruits are harvested throughout most of the year, so that one date is almost as good as another. In any event, accurate information concerning production is available through records of carload shipments.
Corn.—While it is true that some corn is harvested after the first of December, statistics obtained by the Bureau of Agricultural Economics indicate that on the average less than 11 per cent of the corn remains unharvested on that date. It should be further noted that, even though some incompleteness in results as to crop yields may arise from taking the census as early as December 1 or November 1, such inaccuracies are of comparatively small significance because of the fact that yield data are much less important for statistical purposes than data on acreage. Yields vary so greatly from one year to another that a census every five years showing yields gives merely the results of the combination of weather and other crop conditions of that particular year. Furthermore, estimates of yields have become so complete as to provide data practically as accurate as can be obtained by an enumeration, and are usually available about a year before the census is published.
However, in making these estimates of yield correct data on acreage are essential. As pointed out elsewhere, acreage figures constitute a very vital basis for the periodic correction of the basic figures from which crop estimates are derived.
VI. INADVISABIL1TY OP APRIL 1 BECAUSE OF MOVEMENTS OP FARMERS BETWEEN
CHRISTMAS AND APRIL 1
One of the most important objections, however, to taking the census of agriculture on April 1 is that a large proportion of the farmers of the country change from one farm to another and that a large percentage of these changes are made in the period between Christmas and March 1.
The extent of this movement is shown by reference to the following table. This table is based on the results of questionnaires sent to correspondents of the Department of Agriculture in 1926 asking them to report the number of farmers in a block of five adjacent farms who changed farms during the preceding year.
Table 7.—Number and per cent of farmers moving during the crop year 1925-26