The proportionator is the most efficient unbiased stereological method used to estimate population size in samples.
The proportionator is related to the optical fractionator and physical dissector methods that also estimate population.
Unlike these two methods the proportionator introduces sampling with probability proportional to size, or PPS.
The proportionator becomes the optical fractionator if the characteristic is constant, i.e. the same, for all sampling sites.
The proportionator is the de facto standard method used to count cells in large projects.
The increased efficiency provided by the proportionator makes more work intensive methods such as the optical fractionator less attractive except in small projects.
A common misconception in the stereological literature is that design based methodologies require that all objects of interest must have the same probability of being selected.
The optical fractionator is the older standard for estimating the number of cells in an unbiased manner.
The efficiency of a sampling method is the amount of work it takes to obtain a desired CE.
A more efficient method is one that requires less work to obtain a desired CE.
A method is less efficient if the same amount of work results in a larger CE.
(Understand that this might not be efficient if the sampling requires a great deal of work and there is no need for a CE this low.)
In keeping with this notion some amount of effort has been made to perform automatic image acquisition and counting to facilitate the process.
One of the earliest stereological methods that employed PPS was introduced by Walter Bitterlich in 1939 to improve the efficiency of fieldwork in the forest sciences.
Bitterlich developed a sampling method that revolutionized the forest sciences.
It took a considerable amount of time to lay out a rectangle and to measure the trees included in the quadrat.
Lou Grosenbaugh realized the importance of Bitterlich's work and wrote a number of articles describing the method.
Soon a host of devices from angle gauge, to relascope, to sampling prism were developed.
The Bitterlich method, employing PPS, and these devices profoundly increased the efficiency of fieldwork.
Efforts to automate the counting process attack the variance problem at the wrong level of sampling.
Experimental evidence demonstrates that the proportionator significantly reduces the variance between samples, especially in situations where the tissue distribution is heterogeneous.
Another way to look at this is that the proportionator is designed to take the CE reduction issue out of the hands of the researcher.
The application of PPS to cell counting makes larger scale research projects possible, while saving time and reducing expenses.