Car Build Dates Revisited

  By Robert W. Hayne

Chris Henze extracted the following data from an undated article. He obtained it from the January-February 1990 issue of the American Motoring Magazine.  It attempts to correlate the sequence number with a production date.

      In the article Chris makes some assumptions from which he derives a methodology to determine an approximate build date of American Motors vehicle built in the Kenosha plant between August 1968 and July 1969.  Not having access to the original article it is not possible for me to determine if this is actually the Kenosha plant but seems like a reasonable conclusion.  I have expanded the data to include the day of the week and the number of cars built between the dates specified.

      The methodology indicated in Chris's article is good but the assumptions upon which it is based are flawed when the data is carefully examined.  His first assumption is that all the dates represent an end of week but does not specify what the workweek was.  Further he assumes a seven-day work week and that can be seen is not true.  Most end-of-week dates are Fridays but a significant number of others are Saturday.  Production ramp up and termination also introduce non-typical dates and quantities.  A close examination of the data will show some startling information as described in the paragraphs following the expanded data.

AMC production for 1968 and 1969

Day         Date               East Line        West Line      Month/Year

---         ----------        ---------         ---------   --------------

Tues        07-09-1968        E-0000030           W-001018      July 1968

---         ----------                6               2455   --------------

Fri         08-16-1968        E-0000036           W-003473

                                   1183            1865

Mon         08-26-1968        E-0001219           W-005338      August 1968

                                   2399            2788

Fri         08-30-1968        E-0003618           W-008126

---         ----------             2279            2267   --------------

Fri         09-06-1968-       E-0005897           W-010393

                                   2774            3391

Saturday      09-14-1968        E-0008671           W-013784

                                   2891            2894       September 1968

Friday      09-20-1968        E-0011562           W-016678

                                   2914            2884

Friday      09-27-1968        E-0014476           W-019562

------      ----------             2901        --------    --------------

Friday      10-04-1968        E-0017377           W-022376

                                   2851            2877

Friday      10-11-1968        E-0020228           W-025253

                                   2908            2665       October 1968

Friday      10-18-1968        E-0023136           W-027918

                                   3275            3463

Saturday      10-26-1968        E-0026411           W-031381

------      ----------             2921            2874   --------------

Friday      11-01-1968        E-0029332           W-034255

                                   2911            2875

Friday      11-08-1968        E-0032243           W-037130

                                   2915            2742

Friday      11-15-1968        E-0035158           W-039872      November 1968

                                   2916            2887

Friday      11-22-1968        E-0038074           W-042759

                                   1245            1704

Wednesday      11-27-1968        E-0039319           W-044463

-------      ----------             2921            2799   -------------

Friday      12-06-1968        E-0042240           W-047262

                                   2892            2608

Friday      12-13-1968        E-0045132           W-049870

                                   2843            2584       December 1968

Friday      12-20-1968        E-0047975           W-052454

                                      0                  0

Friday      12-27-1968        No Production

------      ----------                0                  0     ------------

Friday      01-03-1969        No Production

                                   2403            2883

Friday      01-10-1969        E-0050378           W-055337

                                   2599            2001

Friday      01-17-1969        E-0052977           W-057338      January 1969

                                   2920            2881

Friday      01-24-1969        E-0055897           W-060219

                                   2922            2575

Friday      01-31-1969        E-0058819           W-062794

------      ----------             2685            2658   -------------

Friday      02-07-1969        E-0061504           W-065452

                                   2912            2666

Friday      02-14-1969        E-0064416           W-068118      February 1969

                                   2804            2917

Friday      02-21-1969        E-0067220           W-071035

                                   2913               0

Friday      02-28-1969        E-0070133           W-071035

      ----------              2913             5518  -------------

Friday      03-07-1969        E-0073046           W-076553

                                   2927               0

Friday      03-14-1969        E-0075973           W-076553

                                   2905            2807 March 1969

Friday      03-21-1969        E-0078878           W-079360

                                   2905            2003

Friday      03-26-1969        E-0081783           W-081363

------      ----------             2330            2168   -------------

Friday      04-04-1969        E-0084113           W-083531

                                   3259            1881

Saturday      04-12-1969        E-0087372           E-085412

                                   2905            3890 April 1969

Friday      04-18-1969        E-0090277           W-089302

                                  3161             2844

Saturday      04-26-1969        E-0093438           W-092146

--------      ----------             2408            2889   -------------

Friday      05-02-1969        E-0096346           W-095035

                                   3207            2775

Saturday      05-10-1969        E-0099553           W-097810

                                   3260            2587

Saturday      05-17-1969        E-0102813           W-100397      May 1969

                                   2801            2877

Friday      05-23-1969        E-0105614           W-103274

                                   2330            2308

Thursday      05-29-1969        E-0107944           W-105574

--------      ----------             2899            2825   -------------

Friday      06-06-1969        E-0110843           W-108399

                                   3233            2799

Saturday      06-14-1969        E-0114066           W-111198

                                   2878            2784 June 1969

Thursday      06-20-1969        E-0116944           W-113982

                                   2897            2827

Friday      06-27-1969        E-0119841           W-116809

-------      ----------             1719            2285   -------------

Thursday      07-03-1969        E-0121560           W-119094

                                    674             2878

Friday      07-11-1969        E-1222324           W-121972      July 1969

                                      0               2166

Thursday      07-17-1969        E-1222324           W-124138

--------      ----------        ---------         --------    ------------

After looking at the statistical data and analyzing it the following facts can be determined:

1      The average number of cars built on the East line during a five-day week is 2,842.

2      The average number of cars built on the West line during a five-day week is 2,784.

3      The average number of cars built on the East line during a six-day week is 3,281.

4      The average number of cars built on the West line during a six day week is 3,581.

5       8/26/1968 was a Monday.  Production ramp up and line shakedown period.

6       9/14/1968 was a Saturday.  East line production is close to five-day average.  Approximately 607 more cars than the five-day average were produced on the West line

7       10/26/1968 was a Saturday.  Approximately 433 more cars than the five-day average were produced on the East line and 697 more cars than the five-day average were produced on the West line.

8       11/27/1968 was a Wednesday.  Thursday the 27 was Thanksgiving.  This week only had three days of production for both the East and West line.

9       4/12/1969 was a Saturday.  Approximately 417 more cars were produced this week on the East line than the five-day average.  The West line was below average.

10       4/26/1969 was a Saturday.  Approximately 319 more cars were produced on the East line than the five-day weekly average.  The West line production was close to the five-day average.

11       5/10/1969 was a Saturday.  Approximately 365 more cars were produced on the East line this week than an average five-day week.  The West line production was slightly below normal for a five-day week.

12       5/17/1969 was a Saturday.  Approximately 418 more cars were produced this week than in an average five-day week.  The West line produced slightly less than average for a five-day week.

13       5/29/1969 was a Thursday and about 512 fewer cars were produced this week on the East line and about 484 fewer cars on the West line.  There were only four days of production this week.

14       6/14/1969 was a Saturday and about 381 cars more than the five day average were produced this week on the East line.  Production on the West line was about normal for a five-day week.

151       6/20/1969 was a Thursday.  A normal five-day week production was accomplished in four days.

16       7/3/1969 was a Thursday.  Four days of production and only 1719 cars were produced.  The end of 1969 production was coming.

17       7/17/1969 was a Thursday.  There was no production on the East line and only 2166 cars produced on the West line.  This is the end of production for 1969 vehicles at this plant.


Considering the facts derived from the data the following can be inferred or deduced:

1      Not all production weeks ended on a Friday and the plant did not run on a seven day per week schedule.  Eleven weeks in the data ended on a Saturday and thirty-six ended on a Friday.  Logic says that the standard production week was five days of two eight-hour shifts.  The extra production required an extra shift/s that was added on Saturday.

2      An average week was composed of five days of two shifts each day.  American Motors produced on average 2842 cars each five-day week on the East line and 2,784 cars per five-day week on West line.

3      An average of 568 cars were produced during each five-day week on the East line and 557 were produced on an average five-day week on the West line

4      An average of 538 cars were produced on the East line in a six-day week and an average of 597 cars were produced on the West line in a six-day week.  There were seven weeks in the two years of production that saw production on a Saturday.

5      The data indicates that when production occurred on a Saturday, both lines were not necessarily open.  For the week ending Saturday 9/14/1968 the East line produced an average number of cars for a five-day week but the West line produced about 290 more cars than average indicating that only the West line was open.  For the week ending Saturday 10/26 1968 the East line produced about 430 more cars than average and the West line produced about 660 more cars indicating that both lines were open that day.  For the week ending Saturday 4/12/69 the East line produced 415 more than the five day average but the West line produced fewer than its five day average indicating that only the East line was open.

      Before the production day can be inferred you must first determine which line on which your car was built and how many days it was in operation.  Once this information is determined the correct divisor can be used to determine day of the week.  If your sequence number begins with an E it was assembled on the East line and if a W the West line.   As an example, my 1969 AMX has a sequence number of E034735.  Therefore it was built sometime during the production week of 11/11 1968.  Subtracting the beginning and ending numbers indicates that approximately 583 cars were produced per day on the East line.  Interpolation suggests that my car was built on Friday the 15th of November 1968.

      The above data and conclusions are based upon hard facts such as dates, Holidays and other items that are easy to determine.  There might be other factors such as a strike although the data would not suggest it.