# E-Waste Reverse Supply Chain: A Review and Future Perspectives
## 4 E-Waste Reverse Supply Chains
### Forecasting Product Returns
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Authors** & **Model Focus** & **Method** & **Variables for Forecasting** & **Product/Equiment** & **Country/Region** \\ \hline [PERSON] et al. [81] & E-waste generation & Population balance model, Webball distribution & The lifespan of electronic equipment, domestic shipments, the number of electronic products owned per household & Eight selected e-waste & South Korea \\ \hline [PERSON] and [PERSON] [82] & Estimating e-waste generation, recoverable materials, potential & Hotys double exponential smoothing and Webball distribution and Monte Carlo simulation & Stock estimation, dynamic lifespans, the assessment of put-on-market & E-waste & Australia \\ \hline [PERSON] and [PERSON] & Estimating the flows and the stocks [88] & Estimate the flows and the stocks of KRT Televisions in 2018-2025 & Dynamic Material Flow Analysis & Improves, Household users, Business and Public, intermediaries & Cathode Ray Tube (CRT) & Peru \\ \hline [PERSON] et al. [84] & Estimating disposal outlets & Material flow analysis & Consumer behaviour, private e-waste trader survey & TVs, washing machine, air conditions, refrigerator, personal computes & Hong Kong \\ \hline [PERSON] and [PERSON] [85] & Estimating e-waste generation in Sao Jose dos Campos city & Survey & E-waste lifespan, disposal profiles, estimated population & Screen selected types of e-waste & Brazil \\ \hline \hline \end{tabular}
\end{table} 
Table 5: _Cont._[PERSON] [77] compared the benefits and drawbacks of five common methods (i.e., Consumption and Use, Simple Delay, Time Step, Mass Balance, and Approximation 2) to estimate the amount of e-waste generation in Jordan. The research concluded that the Consumption and Use approach is widely used in developing nations since variables are required little data and straightforwardly obtained or modified. The Simple Delay approach can be employed to market saturation while the Time Step and Mass Balance approaches are suitable for both saturated and unsaturated markets. The overestimation of e-waste generation is the drawback of the Approximation 2 method but it is suitable for market saturation. The Delay method was utilized in the study of [PERSON] and [PERSON] [78] which aimed to estimate the obsolete mobile phone generation in the years 2010-2020 in the Czech Republic. Their research found that only around 3-6% of obsolete mobile phones in the Czech Republic were collected for recycling and recovery processes. In addition, the amount of obsolete mobile phones in this country will climb up to 26.3 million units in the period 2010-2020. [PERSON] et al. [79] estimated the quantity of e-waste in Ahvaz City, Iran through the Consumption and Use method. They found that air conditioners had the highest percentage of e-waste generation followed by refrigerators, freezers. [PERSON] et al. [80] used combined techniques (such as Weibull distribution, the logistic function, and the population balance model) to forecast the waste quantities of five large household equipment (i.e., TVs, washing machines, air conditioners, refrigerators and personal computers) in Vietnam in the period 2010-2025. The factors for forecasting in this study involve the rate of the disposal using Weibull distribution, the lifespan of electronic equipment, the family size and the sales. The population balance model was also applied in the study of [PERSON] et al. [81] aimed to forecast the waste quantities of eight selected electronic equipment in South Korea. Weibull distribution was also employed to analyse a survey of 1000 families to estimate the average lifespan of electronic appliances. Further, the study estimated the e-waste collection rates for five selected products in the period 2003-2009 and found that in 2009 washing machines had the highest percentage of the collection (28%) whereas the lowest collection rate (7%) was air conditioners.