由于中國內地的嬰兒奶粉曾出現三聚氰胺等質量問題，近年中國內地消費者通過各種途徑直接或間接地搶購中國香港和中國澳門零售市場的嬰兒奶粉，造成港澳當地奶粉市場出現供應緊缺。為緩解當地奶粉供應緊張的狀況，2013年3月1日起，中國香港實行奶粉限購令，打擊跨境平行交易。

請看《中國日報》相關報道：

The government of the Hong Kong Special Administrative Region has cracked down on cross-border parallel trading in infant milk formula to ensure local stores don't run out of stock.The new regulation, starting from March 1, allows a person leaving the city to carry a maximumof two cans, or 1.8 kilograms, of infant formula.

中國香港特別行政區政府已經開始打擊嬰兒配方奶粉的跨境平行交易，以保證當地商店的奶粉供應。從3月1日起實行新規定，離港人士可攜帶凈重不超過1.8公斤(約兩罐)的嬰兒配方奶粉。

為打擊cross-border parallel trading(跨境平行交易)，確保當地infant milk formula(嬰兒配方奶粉)貨源供應，中國香港特區開始實施purchase limits(限購)。盡管有官員表示，99%的mainland-madebaby formula(大陸嬰兒配方奶粉)質量合格，還是有人違反規定去中國香港購買imported milk powder(進口奶粉)。

Parallel trade(平行交易)又稱為counter purchase(互購)或reciprocal trade(對購)，是最簡單、最常用的reciprocity transaction(對等貿易)形式?；ベ徥且环Nspot transaction(現匯交易)，是指一方向另一方出口commodity and/or labor services(商品和/或勞務)的同時，承擔以所得款項的一部分或全部向對方購買一定數量或金額商品和/或勞務的義務。

on the total economy varies with both the level of utilization of labor and capital in the economy at the time of the expenditure, and the segment of the economy which receives the expenditure. If the economy as a whole or the segment of the economy which is the focus of the expenditure is operating at capacity or close to capacity, then the expenditure’s major effects will tend to be inflationary, and will not generate much employment of capital and labor. If the economy or sector is operating at much less than full employment, the expenditure will produce a genuine (non-inflationary) rise in the GNP.

A true measure of the effect of governmental increase in the amount of money made available, then, is not the simple dollar value of the initial injection but the cumulative effect of this injection through spending and re-spending. In the optimum case the initial expansion of income flow could be great enough to produce tax revenues in excess of the original "deficit spending" or the "tax cut", so that deficits are not only smaller than the increased GNP but are recouped. In Keynesian economics the fundamental point of government policy clearly is not budget-balancing but spending in the event of unused productive capacity and unemployment. Spending increases productivity. This productivity resulting from federal spending has overwhelmed the older economic myths of the balanced budget where government is conceived of as just another business firm.

參考譯文：

政府支出對于整個經濟的影響作用，受到以下兩個因素的制約。第一，政府支出之時勞動力和資本的利用情況;第二，接受(政府)支出的經濟部分。如果整個經濟或接受(政府)支出的經濟領域充分地或接近充分地發揮效能，那么政府支出的效果不會很大，所以資本和勞動力也不會得到充分利用。而如果經濟潛能并未充分發揮，政府支出則會真正促進GNP的增長。

對于政府增加支出而產生的效果，真實的衡量標準并非在于最初的支出數額，而在于這一筆開支經過多次投入而產生的長期效果。 在理想的情況下，最初的收入增長產生的稅收會超過最初的“負債投入”或“減免的稅收”。這樣，赤字不僅小于GNP的增長，而且得到了補償。凱恩斯的經濟學理論認為，政府決策的重點并非在于平衡預算，而在于生產能力沒有得到充分發揮，失業率居高不下之時增加支出。 聯邦支出可以促進生產能力這一理論使得傳統的經濟理論受到挑戰。這是因為后者認為政府應發揮類似公司的職能，盡力平衡預算。