markets. Absent currency manipulation or a currency peg, appreciation of the currency can damage other sectors, leading to a compensating unfavorable balance of trade. As imports become cheaper in all sectors, internal employment suffers and with it the skill infrastructure and manufacturing capabilities of the nation. This problem has historically influenced the domestic economics of large empires including Rome during its transition to a Republic in 509 BCE and the United Kingdom during the height of its colonial empire. To compensate for the loss of local employment opportunities, government resources are used to artificially create employment. The increasing national revenue will often also result in higher government spending on health, welfare, military, and public infrastructure, and if this is done corruptly or inefficiently it can be a burden on the economy. While the decrease in the sectors exposed to international competition and consequently even greater dependence on natural resource revenue leaves the economy vulnerable to price changes in the natural resource, this can be managed by an active and effective use of hedge instruments such as forwards, futures, options, and swaps; however, if it is managed inefficiently or corruptly, this can lead to disastrous results. Also, since productivity generally increases faster in the manufacturing sector than in the government, the economy will have lower productivity gains than before. According to a 2020 study, giant resource discoveries led to a substantial appreciation of the real exchange rate. Revenue volatility Prices for some natural resources are subject to wide fluctuation: for example, crude oil prices rose from around $3 per barrel to $12/bbl in 1974 following the 1973 oil crisis and fell from $27/bbl to below $10/bbl during the 1986 glut. In the decade from 1998 to 2008, it rose from $10/bbl to $145/bbl, before falling by more than half to $60/bbl over a few months. When government revenues are dominated by inflows from natural resources (for example, 99.3% of Angola's exports came from just oil and diamonds in 2005), this volatility can disrupt government planning and debt service. Abrupt changes in economic realities that result from this often provoke widespread breaking of contracts or curtailment of social programs, eroding the rule of law and popular support. Responsible use of financial hedges can mitigate this risk to some extent. Susceptibility to this volatility can be increased where governments choose to borrow heavily in foreign currency. Real exchange rate increases, through capital inflows