I want to study the impact of Social Class on Online Shopping Intention or Behavior but it seems inappropriate to ask the social class directly, is there any possibility to determine social class through income or property etc?
The middle class has no commonly agreed definition. Much empirical research tries to operationalize the concept of the middle class employing occupational schemes such as the European Socio-Economic Classification (ESeC) known as the Erikson-Goldthorpe-Portocarero (EGP) Scheme (Erikson and Goldthorpe 1992; Goldthorpe 1987).
Much of the recent comparative research on the middle classes relies on income-based definitions. Typically, being middle class is defined as having an income within a scale constructed around the median and which has typically been symmetric. The definition of the lower cut-off point has a natural link with the poverty threshold, which is set at 50% (OCSE) of the national median equivalised disposable income. Lester Thurow, the first author that adopted this approach (1984), defined the middle class as including households with an income between 75 and 125 per cent of median household income.
Many authors, using a different range of median income, divide the broad category of the middle class into two groups: the lower middle class and the upper middle class (Atkinson and Brandolini 2011; Bigot et al. 2012). Whelan et al. (2016) take those between 60% and 75% of the median to be “precarious” or on the ‘‘margins’’ of poverty. The middle class can then be said to be those not in poverty or in the margins of poverty, between 75% (lower thresholds) and 166% of the median (upper thresholds). Within this they distinguish a ‘‘lower middle class’’ between 75–125% of the median and an ‘‘upper middle class’’ between 125% and 166% of the median. Those whose incomes are at least 167% of the median are considered as the affluent class.
You have basically two possibilities:
(1) Use relative measures. Just use quantiles and split the distribution according to proportional income brackets (e.g., terciles, quartiles, deciles, percentiles).
(2) Use some absolute measure. In this respect, you should find some income brackets in euros irrespective of the country analysed (but, of course, then, adjust for PPP). See, e.g.,
https://www.caixabankresearch.com/en/economics-markets/labour-market-demographics/emergence-middle-class-emerging-country-phenomenon