This thesis mainly concerns two economic methods of measurement. One is the GDP method as a measure of aggregate production in the background of International Comparison Program (ICP). The other is house price index method as a measure of price movements in the context of Sydney house market from 2001 to 2009. Chapter 1 compares hedonic and repeat-sales methods. Repeat-sales price indexes and hedonic price indexes present some different turning points. Also, repeat-sales price indexes depict faster appreciating rates than their hedonic counterparts due to sample bias in repeat-sales methods: repeat-sales samples contain houses with multiple sales, and prices for more frequently sold houses increase faster. Chapter 2 examines the sensitivity and stability of repeat-sales methods. The main results are: first, by changing the definition of ?short interval? between sales repeat-sales indexes fluctuate only to a very limited extent; second, the discrepancy between weighting and not weighting house data for Sydney is not as obvious as for some US cities; third, repeat-sales indexes fall constantly when revised with the extension of data like for some Swedish cities. Chained-repeat-sales method is also proposed. This method makes the repeat-sales indexes move at a slightly softener tempo. Chapter 3 studies the sensitivity of hedonic methods. Time dummy and adjacent period hedonic methods generate similar indexes; while imputation indexes can be relatively volatile. Also, time dummy and adjacent period hedonic indexes are not sensitive to physical characteristic variables such as bedrooms and bathrooms. Observations with physical characteristics recorded generally have higher prices than the whole dataset. Chapter 4 demonstrates the implausibility of the ICP 2005 result for China, and then gives some reasons that likely lead to such results.