Table 3. Dependent and explanatory variables for estimating players’ market value.

Indicator	Variable and abbreviation
Dependent variable	Transfermarkt’s market value (training) and Transfer fees (model error)
Player characteristics	Position (P), Footedness (FT), Age, Height (H), and Continent (Cnt)
Player performance	Playing time (PT), Aerial duel accuracy (ADA), Tackle accuracy (TA), Shots intercepted (SI), Fouls (F), Yellow cards (YC), Red cards (RC), Goals (Gls), Shots (S), Shot accuracy (SA), Assists (A), Dribbles (Dr), Crosses (Cr), Corners (C), Passing accuracy (PA), Short-pass accuracy (SPA), Long-pass accuracy (LPA), Key passes (KP, passes that create shots for teammates), Progressive passes (PP, passes that move the ball to the opponent’s goal), Deep passes (DP, passes into the space between defenders), Passes in the penalty area (PPA), Passes in the last quarter of the opponent’s half (PLO), and Free kicks (FK)
Labour and club characteristics of the players	Contract (Ct) and League
Popularity indicators	GTA, PC1, Mean (Mn), Median (Mdn), Maximum (Max), Minimum (Min), and Standard deviation (Sd)