Metropolitan areas in Czech Republic are defined by the Czech Statistical Office as aggregates of municipalities (LAU1). However, because reported data are insufficient at that level, Moody's Analytics has elected to define our own metro areas as aggregates of NUTS 2 and NUTS 3 areas.  We have picked four:

• Prague
• Ostrava
• Brno
• Plzen

According to the ESPON Project, the Prague metro area comprises the bulk of the populations of the Prague and Central Bohemia NUTS 2 areas.  The other three Czech metros of interest, Brno, Plzen and Ostrava, comprise the bulk of the populations of their respective NUTS 3 areas (Brno 66%, Plzen 64%, Ostrava 92%).  Thus we feel that our choices constitute satisfactory proxies.

References:

Table 1 of 1. Metropolitan areas in Czech Republic. We define each of our metropolitan areas as aggregates of either NUTS 2 (region / obvodi) or NUTS 3 (district / okresi) areas.

The Czech Republic has a national geo code of ICZE, all codes for its geographic subdivisions use ICZE as a prefix, and all Moody's Analytics metro areas feature the letter "M." Each of the four areas is identified as ICZE(underscore)M(letter)(letter)(letter), and may be retrieved in bulk with the basket geo wild card ICZE_M^^^.