T.R. MALTHUS, 1766-1834

English clergyman, Thomas Robert Malthus, was the first person to draw widespread attention to the two components of natural increase, births and deaths (fertility and mortality).

IN HIS ESSAY ON THE PRINCIPLE OF POPULATION, INITIALLY PUBLISHED IN 1798, MALTHUS POSTULATED THAT POPULATION TENDED TO GROW GEOMETRICALLY (EXPONENTIALLY) WHILE THE MEANS OF SUBSISTENCE (FOOD) GREW ONLY ARITHMETICALLY.

THE MALTHUSIAN TRAP

ARITHMETIC GROWTH (FOOD): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10…

GEOMETRIC GROWTH (POPULATION):1, 2, 4, 8, 16, 32, 64, 128, 256, 512…

MALTHUS ARGUED THAT THE DIFFERENCE BETWEEN GEOMETRIC AND ARITHMETIC GROWTH CAUSED A TENSION BETWEEN THE GROWTH OF POPULATION AND THAT OF THE MEANS OF SUBSISTENCE.-- THIS GAP COULD NOT PERSIST INDEFINITELY.

OWING TO WAR, DISEASE, HUNGER, AND VICE, MORTALITY WOULD SERVE AS A POSITIVE CHECK ON POPULATION GROWTH.

SOLUTION TO THE MALTHUSIAN TRAP

Preventive checks: birth control through (1) later age at marriage.

(2) abstinence from sex outside marriage. (Malthus opposed artificial methods of birth control on moral grounds. Viewed contraception as a vice)

POPULATION EXPLOSION

Contrary to Malthus’s prediction, mortality has not yet risen to curb world population growth.

< 1 billion people in 1800 6 billion by the end of the 20th century

POPULATION EXPLOSIONWhy was Malthus unable to foresee the population explosion (also known as the population bomb)?

He did not recognize the force of the Industrial Revolution, which produced exponential growth in the means of subsistence.

THE DEMOGRAPHIC TRANSITION

The demographic transition framework illustrates population growth in terms of discrepancies and changes in two crude vital rates – mortality and fertility (ignores migration)

تئوری انتقال جمعیتی) چرخه جمعیت شناسی(

اساس این تئوری همه جمعیتها در گذشته سطح باالیی

از مرگ و میر و زاد و ولد داشته اند ( رشد جمعیت ناچیز)

ولooل تحooتي (مراحooذار جمعيooل گooمراح)جمعيتي

كoه داراي يoا جامعoر جoد جمعيت در هoرش مرحلoه اي مي 5چرخoه جمعيت شoناختي

باشد.1- د وoيزان مواليoت هم مoه نخسoدر مرحل

هم مoooيزان مoooيرايي جمعيت زيoooاد مي باشooد و چooون اين دو پديooده همooديگر را خنooثي مي كننooد تعooداد جمعيت تقريبooا

35-45( تعoادل در حoدود . نoدثoابت مي مoادر هزار)

2- عيتooود وضooه علت بهبooه دوم بooدر مرحلاقتصoادي(ماننoد انقالب كشoاورزي در هoزاره هoooooاي قبoooooل از ميالد و انقالب صoooooنعتي اروپoا)مoيزان مoيرايي رو بoه كoاهش مي گoذارد در حاليكoه مoيزان تولoد همچنoان بoاال مي باشoد كooه نتيجooه آن افooزايش روز افooزون جمعيت خواهooد بooود.در هooزاره جديooد علت افooزايش جمعيت در آسoياي جنoوب شoرقي و آفريقoا

چنين پديده اي مي باشد.

3- :ومooه سooير مرحلooرگ و مooاي مooميزانهكoاهش مي يابoد و ميزانهoاي تولoد هم رو بoه

كاهش مي گذارد. الooooوز جمعيت در حooooال هنooooدر همين ح

افoزايش خواهoد بoود.ايران در حoال حاضoر در چنين مرحله اي قرار دارد.

4- :ارمoه چهoد كم مي مرحلoاي تولoميزانه مoرگ هم بoاقي مي یشoودو در ضoمن تعoداد

مانooد در نتيجooه مقooدار جمعيت ثooابت مي مانoد.در اين مرحلoه مoيزان رشoد جمعيت بoه

. ه استصفر رسيدارoooتان،دانمoooكکدر انگلسoooد و بلژيoooرش

( تعoادل .اسoت)در هoزار 1/0جمعيت نoا چoيز ( در هزار)10-15در حدود

5- :ه پنجمooتر مرحلooاز هم كمooه علت بooبشooدن مooيزان تولooد هooا و پooايين تooر بooودن مooيزان تولooد از مooيزان مooرگ مooيزان رشooد جمعيت منفي مي شooود.در سooالهاي آخooر

ارستانمجدر آلمان و 1980دهه

FIGURE 2 THE DEMOGRAPHIC TRANSITION

Source: Joseph A. McFalls, Jr. Population: A Lively Introduction. Third edition. Population Reference Bureau 53(3); 1998: 39

CRUDE VITAL RATES

Crude Birth/Death Rate =

# births/deaths in calendar year * k

mid–year population

Rate of Natural Increase =

CBR - CDR

FIGURE 3 -DEMOGRAPHIC/ EPIDEMIOLOGIC TRANSITION FRAMEWORK

Source: Ian R.H. Rockett. Population and Health: An Introduction to Epidemiology. Second edition. Population Reference Bureau 54(4); 1999: 9