【正文】
wnward trend over extended periods. In additon, building the model so that the ratio is eventually constant makes the analysis much simpler. Assuming that A multiplies L is therefore very convinient . ? The central assumptions of the solow model concern the properties of the production function and the evolution of the three inputs into production (capital, labor, and knowledge) over time. We discuss each in turn. ? Production function ? It has constant returns to scale in its two arguments, capital and effective labor. That is , doubling the quantities of capital and effective labor (for example, by doubling K and L with A hild fixed) doubles the amount produced. ? More generally, multipling both arguments by any nonnegative constant causes output to change by the same factor. ? F(cK,cAL)=cF(K,AL) ? The assumption of constant returns allows up to work with the production function in intensive form. Setting c=1/AL in equation yields ? Y/AL = F(K/AL,1) ? y = f(k) ? 狀態(tài) ? 這些假定都與凱恩斯主義的論點(diǎn)相反,而與傳統(tǒng)經(jīng)濟(jì)學(xué)的觀點(diǎn)相近。哈-多模型、索洛模型都以凱恩斯的消費(fèi)理論為基礎(chǔ):假設(shè)一個外生給定的儲蓄率。這個來源于里昂惕夫型生產(chǎn)函數(shù)( Leontief,1941)的苛刻條件極大地限制了哈羅德-多馬模型的解釋力。解 P/Y得: wpwwp sssYIssYP?????1? 上式表明,利潤占收入的總份額是投資產(chǎn)量的函數(shù) ? 瓊 .羅賓遜把卡爾多的模型做了新解。 ? 下面僅就卡爾多經(jīng)濟(jì)增長模型為例進(jìn)行說明。劍橋?qū)W派經(jīng)濟(jì)增長模型認(rèn)為儲蓄傾向是可變的:劍橋增長模型把社會成員分為利潤收入者和工資收入者兩個階級,其儲蓄都占有各自收入的一個固定比例,但利潤收入者的儲蓄傾向大于工資收入者的儲蓄傾向,有時甚至還象古典經(jīng)濟(jì)學(xué)家那樣把工資收入者的儲蓄傾向假定為零。由于他們都執(zhí)教于英國劍橋大學(xué),故稱作劍橋經(jīng)濟(jì)增長模型。他認(rèn)為由投資決定的當(dāng)期的經(jīng)濟(jì)增長率 G和由上一期的收入(準(zhǔn)確地說是上期收入所引致的儲蓄)與技術(shù)水平?jīng)Q定的經(jīng)濟(jì)體自身能力所提供的增長率 Gw之間的均衡,是實(shí)現(xiàn)均衡增長的關(guān)鍵。這里需要說明一下,索洛模型常被稱為新古典增長模型,但這里所謂的“新古典”是指借用了馬歇爾思想的新古典(在這一點(diǎn)上,它類似于新古典綜合派),而不是新古典宏觀經(jīng)濟(jì)學(xué)的“新古典”,因?yàn)楹笳呤且苑磩P恩斯主義的身份出現(xiàn)的。Cc 15 solow growth model 索洛增長模型 模型的凱恩斯主義基礎(chǔ) ? 哈羅德-多馬模型、劍橋模型和索洛模型都是建立在凱恩斯主義基礎(chǔ)上的。只有了解了這三個經(jīng)濟(jì)增長模型之后,才會對凱恩斯的思想有一個較為完面的認(rèn)識。 一、哈羅德-多馬模型 ? 哈羅德的分析以凱恩斯的國民收入均衡理論為基礎(chǔ),與凱恩斯的比較靜態(tài)的分析方法不同,他對經(jīng)濟(jì)增