The model was created with LOESS on the mean fieldwork of the polls. Elections, exit and Euroelection polls (lower turnout rate than the response rates of polls), as well as polls with unclear fieldwork dates were excluded from the model (shown as empty rings in the graph). Note that one of the pollsters (ÚVVM) has only done polls of party "sympathies" following the elections (late 2002-2003; late 2006-early 2007). Due to sparse data from these periods, these polls were used despite it not being clear how much they are compatible with the usual ones. Similarly, the 1998-2000 period was fitted separately due to lower data quality. The model's smoothing was optimised using the Mean absolute confidence percentage error on each period separately.