Table 1 Definition of variables

A. Dependent variable

REV

Income diversification index

\(1 - \left[ {\left( {\frac{{{\text{NON}}}}{{{\text{NETOP}}}}} \right)^{2} + \left( {\frac{{{\text{NET}}}}{{{\text{NETOP}}}}} \right)^{2} } \right]\)

Brighi and Venturelli [4], Chiorazzo et al. [5], Ferreira et al. [11], Mercieca et al. [23], Sanya and Wolf (2011), Stiroh [30], Stiroh and Rumble [31]

B. Independent variables

SIZE

Bank size

Log (Total assets)

 + 

DeYoung and Rice [7], Duho et al. [9], Meng et al. [22], Mercieca et al. [23], Nguyen et al. [24, 25]

SIZE1

Bank size

Bank with total assets of less than VND 100 billion = 1; otherwise, 0

−

Chiorazzo et al. [5], DeYoung and Rice [7], Hidayat et al. [15], Lepetit et al. [20, 21], Mercieca et al. [23], Nguyen et al. [24]

C. Control variables

EQT

Ratio of equity to total assets

\(\frac{\mathrm{Total\, equity }}{\mathrm{Total \,assets}}\)

 + 

Ho and Vo [16], Meng et al. [22], Nguyen et al. [24, 25]

LA

Loan ratio

\(\frac{\mathrm{Total\, outstanding\, loans\, to\, customers}}{\mathrm{Total\, assets}}\)

−

DeYoung and Rice [7], Ho and Vo [16]

DPS

Capital mobilization rate

\(\frac{\mathrm{Total\, mobilized\, capital\, from\, customers}}{\mathrm{Total\, liabilities}}\)

−

Ho and Vo [16]

LIQ

Liquidity ratio

\(\frac{\mathrm{Liquid\, assets}}{\mathrm{Total\, assets}}\)

−

Duho et al. [9], Meng et al. [22]

NIM

Net interest margin

\(\frac{\mathrm{Net\, interest\, income }}{\mathrm{Total\, earnings\, asset}}\)

−

Ho and Vo [16], Lepetit et al. [21], Nguyen et al. [24, 25]

EFF

Cost efficiency

\(\frac{\mathrm{Total\, operating\, costs }}{\mathrm{Total\, revenue}}\)

−

Ho and Vo [16], Nguyen et al. [24, 25]

NPL

Nonperforming loans

\(\frac{\mathrm{Total\, nonperforming\, loans}}{\mathrm{Total\, loans}}\)

 + 

Nguyen et al. [24]