Because of the large number of roughly comparably sized private and public firms, the petroleum industry provides a laboratory for exploring differences between private and state owned enterprises in related businesses. Without passing judgement on if it has to be that way, it appears as though the private firms are vastly more efficient:
Efficiency differences between private and state-owned enterprises in the international petroleum industry (1992)
Technical (managerial), scale and allocative efficiency differences
between private and state owned firms in the international petroleum
industry are estimated. The estimation of Aigner-Chu deterministic
frontiers, maximum likelihood stochastic frontiers, and maximum
likelihood Gamma frontiers make this analysis the most complete and
sophisticated testing of property rights theory available. The
empirical findings suggest ceteris paribus, that state firms could
satisfy the demand for their output with something less than half of
their current resource inputs simply by being converted to private,
for profit enterprises.
Of course, that last claim depends on the costs of privatization and asserting those efficiency gains can actually be realized in the sorts of places where oil firms are state owned.
The Financial and Operating Performance of Newly Privatized Firms: An International Empirical Analysis (1994)
This study compares the pre- and postprivatization financial and
operating performance of 61 companies from 18 countries and 32
industries that experience full or partial privatization through
public share offerings during the period 1961 to 1990. Our results
document strong performance improvements, achieved surprisingly
without sacrificing employment security. Specifically, after being
privatized, firms increase real sales, become more profitable,
increase their capital investment spending, improve their operating
efficiency, and increase their work forces. Furthermore, these
companies significantly lower their debt levels and increase dividend
payout. Finally, we document significant changes in the size and
composition of corporate boards of directors after privatization.
Some evidence from a broader array of industries:
Ownership and Performance in Competitive Environments: A Comparison of the Performance
of Private, Mixed, and State-Owned Enterprises (1989)
The coefficients for MEs [Mixed Ownership Enterprises] and SOEs [State Owned Enterprises] are negative and statistically
significant at the .05 level for a one-sided alternative in all
equations, which indicate that, on average, MEs and SOEs are
significantly less profitable and less efficient than PCs [Private Corporations] after
controlling for the factors described above. On average, SOEs have a
return on equity of almost 12 percent less than PCs ; they have a
return on assets and a return on sales that are about 2 percent less
than PCs, and their net incomes are \$66 million less than PCs. MEs
perform worse: their return on equity is more than 12 percent less
than PCs, their return on assets and return on sales are about 3.5
percent less than PCs, and their net income is \$165 million less than
that of PCs. In terms of sales per asset, both SOEs and MEs fare
equally poorly relative to PCs; but in terms of sales per employee,
SOEs are less efficient than MEs.
A more recent result:
State-Owned and Privately Owned Firms: An Empirical Analysis of Profitability, Leverage, and Labor Intensity (2001)
The results of the comparison strongly support the proposition that
government firms display inferior profitability. ... We test an implication
of the Boycko et al. (1996) model that government firms will tend to
use more labor than their private counterparts. Cross-sectional
comparisons support the model
state-owned-enterprisesandprivatisationtags? $\endgroup$