Based on the QLMUS as well as the NOMUS and MUS in 1981-2000, the research aims (1) to characterize QLMUS in terms of sample selection and attrition due to match and (2) to assess the representability and estimation effectiveness of QLMUS in comparison to MUS and NOMUS. Main findings: First, attrition due to match does have a salient effect on the selectivity of QLMUS in which the age of samples is associated with a concave effect and education with a negative effect on match rate. Second, the match rate of QLMUS is seen to exhibit distinct spatial disparities, with the highly urbanized areas having lower match rate. This phenomenon is highly likely due to geographic migration. Third, on the basis of labor force participation rate (LFPR), unemployment rate (UR), turnover rate (TR), and wage , LFPR estimated from the QLMUS, NOMUS basically are compatible at all for the period of 1981-90, the estimates of UR from the three data sets are mostly not compatible, while the estimates of TR and wage from the QLMUS, NOMUS, and MUS are compatible at all.