Stamp Tax

Stamp taxes are payable by the purchase and use of stamps and have been required in the issuance, sale, or transfer of stocks and bonds; conveyances of real estate, sales of playing cards, and issuance or renewal of foreign issuance policies; and even in silver bullion transfers. Payment of stamp taxes can be evidenced by placement of the appropriate stamp on the stock, bond, or memorandum of sale or, for instance, on the back of playing card packs.

Stamp taxes are very certain forms of taxation, and proof of payment is demonstrated by the physical stamp or memorandum. Stamp taxes are really just another form of excise tax, and their individual validity can be adjudged in the same way.

TEXT 5

First, the differences in crude birth rates between the two groups of countries are not due to differences in the age structure of women within the childbearing ages, or in the shares of these women in total population. Adjustments for proportion of women and for their age structure have only minor effects: the gross reproduction rates are above 2.0 for almost all the LDCs*, and are below 2.0 for all the DCs**.

Second, the difference in incidence of marriage (including consensual) is significant only for women under 25 years of age. In these early ages the proportions of married women to all women are distinctly higher in the LDCs than in DCs, but the differences disappear in the older groups. With a rough allowance for disparities in intramarital fertility (for the age 15-19 age class assumed to be zero, and for the 20-24 age class assumed to be about halfway between zero and the relative difference in the 25-29 age class), the difference in marriage incidence accounts for about a quarter of the total disparity in crude birth rates between LDCs and DCs – an estimate that is perhaps on the high side.

Third, there are wide differences in intramarital fertility in the two age classes of women that markedly affect the total birth rates – 25-29 and 30-34.The differences for these two age classes contribute about one-half of the total difference in crude birth rates between the two groups.

Fourth, the relative, though not the absolute, difference sin intramarital fertility continue to rise for older women still in their childbearing period, 35 and over. As much as a quarter of the total difference in crude birth rates between the LDCs and DCs is accounted for by the continuation of fairly high fertility beyond female age 35 in the former and by the rapid decline of fertility of the older women in the latter.

* Less Developed Countries

** Developed Countries

TEXT 6

ECONOMIC ASPECTS OF FERTILITY TRENDS

Finally, this prevalence of higher fertility in the LDCs associated with earlier marriages, with much higher intramarital fertility in the major childbearing ages below 35, and the continuation of childbearing to more advance ages beyond 35 results in distinctive characteristics of both births and parents in the LDCs compared with the DCs. First, the share of higher order births in total births is larger the LDCs than in the DCs. Indeed, over one half of the difference in the crude birth rates between the two groups of countries is accounted for by births of fifth or higher order. Second, parents, particularly fathers, of a substantial proportion of newborn children are older in the LDCs. Thus in countries with per capita product below $ 200 (in 1958), one-fourth of the children born had fathers 38 years old or older, and the birth rates specific to this age group was 120 per thousand; whereas in the high income countries, one-fourth of total births had fathers only 35.7 years old or older, and the specific birth rate was 30 per thousand.

This persistence of higher fertility for a long time span within the family life cycle, which means large household units and many families with young children and fathers advanced in age, is one set of characteristics of the fertility pattern of the LDCs relevant to any explanation of economic causes and effects. The second, only barely touched upon, is the clustering of fertility measures around a high average in the many LDCs, matched by a similar though less concentrated clustering of fertility measures around a low mean in the DC. Crude birth rates in the LDCs range from the high 30’s upward, are mostly above 40 per thousand, and rise to the high 40’s, whereas those for the DCs cluster between 16 and 20 for the “older” countries of Europe and Japan, and between the lower and upper 20’s for the “young” and open countries like the United States, Canada, and the USSR.

* Less Developed Countries

** Developed Countries

TEXT 7

The centrifugal pump is one of the simplest pieces of equipment from the controls and instrumentation point of view. It is a two port device with a well defined characteristic. Its purpose is to provide the necessary pressure to move liquid at the desired rate from point A to point B of the process. Figure 1-1 shows a “generic” process with a centrifugal pump connected to deliver liquid from A to B.

Figure 1-2 shows the characteristic curve of an actual pump (a single stage vertical turbine pump) together with the characteristic curve of the process, known as the system curve. The intersection of the two curves defines the operating point of both pump and process. It would be fortunate indeed if this operating point is the one actually specified for the process. It is impossible for one operating point to meet all desired operating conditions since the operating point, is, by definition, exactly one of an infinity of possible operating points. In fact the entire point of controlling the pump is to modify its characteristic so that its actual operating point is the one that is required at every instance in time.

The minimum static differential pressure of the process is frequently zero, as in a closed, circulating system. If the pump is in parallel with other pumps that are maintaining the system pressure, then P_lm is greater than zero. It is clear from the outset that if P_pm , no amount of process control can force the two curves to intersect. The pump is simply inadequate. How is process control like cutting off a rope? You can always cut off more, but you can’t cut off less.

Assuming the pump is more than adequate for the process requirements at the moment, what is the best way to trim it back to the desired operating point, P₁, Q₁? There are three possible locations to place in a valve: at the discharge, at the suction, and as a recycle valve. Each will be discussed in turn.

TEXT 8

MEASUREMENT

The appropriate measurement for the controller depends on the demands of the process. Flow control is a frequent requirement. Two rules guide the location of the flow measurement: make sure that side streams are included or not, as required, by the measurement and make the measurement at the highest convenient pressure. The latter requirement is to avoid any possibility of flashing or cavitation within the measuring device. In general the best place to measure flow from a centrifugal pump is between the recycle Tee and the discharge throttling valve. The exception is when the discharge is at extremely high pressure and the suction has adequate NPSHA. In that case a suction measurement may be the best.

Level control of a vessel is one of the most common requirements. The vessel may be either upstream or downstream. It is quite possible to connect the Level Controller directly to the discharge valve. Frequently, however, the vessel serves to buffer a downstream process from upstream flow variations. In that case it is not desirable for level control to be precise. Perfect level control implies that the flow out is exactly equal to flow in at all times. Often it is desired that the downstream flow remain as uniform as possible while keeping the level within bounds. In simple terms, it is desired that the flow out is the average of the flow in. The vessel absorbs the instantaneous differences. This simple requirement is more difficult to accomplish than it may seem and deserves a discussion entirely of its own. A simple arrangement that is often satisfactory and is widely used is to have the Level Controller cascade to a Flow Controller on the pump discharge. The flow loop keeps the discharge ‘constant’ while the Level Controller gradually raises or lowers the setpoint as the level in the vessel rises or falls.

TEXT 9

At the far end of the system curve the pump curve and the system curve are almost parallel. (the particular pump chosen for this example has a rather steeply rising curve near shutoff. Most are considerably flatter). In mathematical terms this means that the intersection is poorly defined. In practical terms it means that it is difficult to maintain a precise operating point and that control is ‘loose’ at high turndown.

In practice, variable speed drives for centrifugal pumps are still relatively uncommon. For small pumps the power savings are not significant and for large pumps the associated electronics become very expensive. Also, they do not have the high reliability of valves. Variable speed stream turbine drives are quite common in the larger horsepower ranges. Electric variable speed drives are use din certain specialized application such as pumps that are embedded inside a high pressure vessel. In such cases there are no alternatives.

RIDING ON THE CURVE. Last but not least: No control at all! The fact is that the majority of pumps in the world run with no control at all. The exact flows and pressures are not critical and the pump has been reasonably well selected. The discharge pressure will rise to partially compensate for increased back pressure. It falls as the back pressure decreases so that the flow does not increase as much as it otherwise might. The pump is allowed to “ride on its curve”. When this situation is acceptable, leave well enough alone and don’t try to fix what ain’t broke. (Be careful, though, the machine may still require minimum flow and other protections as detailed in the section on Machine Protection).