Levensduur en sloop van personenauto's in Nederland, 1950–1964*

Summary The life distribution of motorcars is examined over the period from 1950 to 1964. Age-specific survival rates, derived from Dutch registrations, are averaged and lead to the life table shown in table 4. The deviations from average age-specific survival rates show no significant variation over time nor over successive car generations. Since the registrations include an increasing number of used cars imported from Germany this apparent stability hides compensating changes in car scrap page. Since before the war the life expectancy of motorcars has increased from 8 to 11 years, and it is argued that this is due to the widening of the used car market. In the next stage, which is already well under way in Germany, new cars replace used cars, and rising apparent scrappage rates reflect the disposal of the latter by export.     

De gemiddelde bezetting van personenauto's in interlokaal verkeer*

Summary This paper, read in Utrecht on October 14th 1965, deals with the average occupancy of cars outside urban areas. During the years 1962 and 1963 more than 500 samples (each consisting of 150 cars) have been taken on two points of the dutch road-system. The samples covered the different months, days (sundays, Saturdays and week-days) and hours (except those without daylight). The average occupancy turned out to be 1.8 on week-days (with a minimum of 1.4), 2.5 on Saturdays (with a minimum of 2.1) and 3.1 on Sundays (the over-all average for all days being 2.1). These results seem to be representative for the whole dutch car traffic as is shown by comparison with observations on other points and other data. Comparison of the seasonal, weekly and hourly patterns of the average occupancy with those of the car traffic density enable to draw conclusions about the responsibility of different kinds of traffic (commercial and commuter traffic versus social traffic) for congestion and for the construction and maintenance cost of the road-system.     

Een toepassing van “importance sampling”

Summary This paper describes an experiment with “importance sampling”, to show how much reduction of the computation time and sample size can be achieved in comparison with the usual Monte Carlo method. A comparison is made between each of the three methods of “importance sampling” and the usual Monte Carlo method by the determination of the expression Of the three methods A, B and C the first one uses the shifted exponential distribution, the second one uses the gamma distribution, and the third one uses the exponential distribution with modified parameter. These three methods have all smaller variances, ranges and sample sizes than the usual Monte Carlo method. Their order of preference is A, B, C. With respect to computing time only the method A is significantly better. So only the method A is an improvement in respect of both the sample size and the computing time.     

Autoverkopen en autopark in Nederland, 1950–1970

Summary This is a study of the demand for the ownership of new or firsthand cars, i.e. the demand of ‘first owners’ who habitually buy new cars which are then traded in long before they are obsolescent. Upon combining the evidence of various surveys with time-series for 1950-64 it is found that this ownership has an income elasticity of 2 and a price elasticity of – 1.25 in respect of the constant-quality index of new car prices earlier provided. On the average new cars are traded in after three years so that roughly one third of the existing stock is replaced every year. These values together determine an equation for purchases of new cars which accurately predicts new registrations in 1965 and 1966. Projections for the years 1967-70 are provided. In the model employed the total number of cars (including used cars) is determined by the active demand exerted by ‘first owners’ on one hand and by the hitherto fairly constant scrappage rates on the other. Projections of the overall ownership rate can therefore be derived from the forecasts of new registrations. The ownership rate will approach 80% around 1970, and it is likely that at that stage the current scrappage rates will cease to apply in view of the greater predilection for comparatively younger cars.     

Strikes and strike trends in West Germany, 1950–78

During the 1970s West German social scientists began to pay more attention to the strike phenomenon. In this article the author reviews recent research contributions in the Federal Republic and analyses the quantitative and qualitative aspects of strikes over the last thirty years.     

Een Monte-Carlo-bepaling van overschrijdingskansen, in verband met een keuzetest

A Monte-Carlo method for a test of significance, applied to points on a lattice, in connection with a vocational preference test, by C. A. G, Nass.
Appendix by Constance van Eeden.
A periodical rectangular lattice, with a period of k.m, is considered. Thus there are N = k.m points on the lattice, repeated in the two perpendicular directions. Two points are said to be "connected" if they are adjacent in a straight or diagonal way. Thus, if k and m 3, every point is connected with 8 other pooints. Out of the N points of the lattice, n points are selected and the total number of connections x, of all possible pairs of those n points is considered for a vocational preference test with k = m = 9, N = 81, n = 10. The problem is to test whether the sum y = x₁+…+ x*** from a sample of h values of x, is significantly small, under the hypothesis that in the h cases the n points are selected at random with equal chance. A Monte-Carlo sample of 100 values of x was taken, using random numbers. For h = 1, the problem was solved by the determination of P( y x₁), assuming that y is taken at random from the 101 values of x, supplied by the Monte-Carlo sample and x₁ for fixed values of x₁. For h - 2, a similar solution is given. For greater values of h, Student's two-sample test, with correction for continuity is suggested. For h = 2 the results of Student's test are compared with those of the solution mentioned above.
In the appendix a summary is given of results found by P.A.P Moran and P. V. Krishna Iyer for some closely related problems. Further some results concerning exact distributions, moments and asymptotic distributions for C. A. G. Nass' problem are given. The proofs of these results may be found in a paper by C. van Eeden and A. R. Bloemena (1959).     

On Testing Conditional Sigma – Convergence*

In a cross‐section where the initial distribution of observations differs from the steady‐state distribution and initial values matter, convergence is best measured in terms of σ‐convergence over a fixed time period. For this setting, we propose a new simple Wald test for conditional σ‐convergence. According to our Monte Carlo simulations, this test performs well and its power is comparable with the available tests of unconditional convergence. We apply two versions of the test to conditional convergence in the size of European manufacturing firms. The null hypothesis of no convergence is rejected for all country groups, most single economies, and for younger firms of our sample of 49,646 firms.